How the clashes happened:
11.30: When two police serve arrest warrants on three red-shirt leaders at the Rajprasong intersection, a table holding Buddha images collapses, causing a red image of the Emerald Buddha of the protesters to break into two. Red-shirt guards rush to cover the broken Buddha image with sheets of newspaper and do not allow photos to be taken.
11.45: Some red-shirt leaders alert protesters about a possible crackdown by troops. The leaders, including Wisa Khanthap, Kwanchai Praiphana and Phaichit Akksornnarong, tell the protesters that they learned that troops were advancing on the Phan Fa rally site.
Protesters use pickup to block five accesses to the main rally site - Democracy Monument, Wanchart Bridge, Larn Luang intersection, Pom Prakarn intersection and Misakawan intersection.
12.50pm: Red shirts, led by Kwanchai, move from Phan Fa Bridge to the First Army Area headquarters on Rajdamnoen Nok Road, claiming they want to demand the Army to stop serving the government.
When they try to storm the compound, soldiers close the gates and train water cannons on them. The protesters throw pieces of wood at the troops before retreating to a site nearby, the Sue Bah area. Reporters say gunshots were heard coming from the area.
1.00: A reporter says protesters and soldiers clashed at Misakawan intersection on Rajdamnoen Nok Road. Soldiers fired guns into the air to disperse a group of protesters, up to six of whom were wounded. A company of soldiers doubled back to the King Chulalongkorn Monument to cut off a group of protesters. Soldiers had moved to Makkhawan-Rangsan intersection, in front of the United Nations building.
1.20: Hundreds of riot police are deployed at Ploenchit intersection while red-shirt leaders call for the protesters to form barricades to counter police.
TV footage shows police in full gear marching to Ploenchit, which is near Rajprasong, the venue occupied by red shirts for days. The deployment indicates that the government plans to disperse the pro-Thaksin protesters.
Red-shirt leaders tell the protesters to wake up and come out of their tents. They distribute handkerchiefs to protect the protesters from tear gas.
The leaders call for red shirts upcountry to go to their city hall and do whatever they want.
1.50: Protesters and soldiers clash again when the Army shoots tear gas and water at the red shirts who tried to raid the First Army Area headquarters on Rajdamnoen Nok Road.
The operation pushes the protesters back to the Misakawan area nearby. A protester is hurt.
2.00: Department stores around Rajprasong begin to close early amid the tense situation.
2.10: Some 1,000 troops from the First Army Area head to Phan Fa Bridge.
The troops march past the Education Ministry to Makkhawan-Rangsan Bridge.
A helicopter flies over the area. Officers tell non-protesters to leave.
Red-shirt protesters confront three companies of Border Patrol police at the Chidlom intersection.
The police had approached from the Asoke intersection past Ploenchit to the Chidlom intersection, where protesters rushed to try to push them back.
Police are armed with only shields and batons. Outbound lanes of Sukhumvit Road are closed.
2.20: Troops fire tear gas at protesters at the Misakawan intersection.
At the Phadung Krung Kasem Canal, troops move forward and turnwater cannon on the protesters. Some leaders on stage there are arrested.
2.30: Four Skytrain stations suspend operations. Passengers are told to use nearby stations as authorities are preparing to disperse the red shirts at Rajprasong. The four stations are Rajdamri, Siam, Chidlom and Ploenchit.
2.35: Troops push red-shirt protesters from Makkhawan-Rangsan Bridge in the direction of Phan Fa while starting to fire tear-gas canisters.
Protesters retreat, as they are not wearing any gear to protect themselves from the gas. Several have
runny eyes. Troops have crossed over Makkhawan-Rangsan.
2.50: Troops have already seized control of the area in front of the Kurusapa Auditorium at the Education Ministry, Modernine TV reports.
Military officers urge protesters through loudspeakers to go home.
The protesters stand on both sides of the canal while the troops maintain their position in front of Kurusapa hall.
3.15: Former prime minister Thaksin Shinawatra sends an SMS to his followers' phones using TSLive, which reads "Abhisit has ordered to suppress protesters and urged people to help protesters. Democracy and justice must be real".
3.20: Some 1,000 troops advance from the Royal Plaza to Makkhawan Bridge. The red shirts try to prevent them from proceeding to the Chor Por Ror intersection. The two sides confront each other at Makkhawan Bridge.
3.30: Hundreds of troops arrive at the bridge to reinforce those already there. Armed with batons and shields, they form lines to keep people from entering the rally area.
3.45: About 1,000 soldiers seize Makkhawan Bridge by firing bullets and tear gas into the air. Protesters run back as the fumes spread.
The soldiers line up and walked towards the protesters to reclaim the area. Protesters fight to take the area back while soldiers do not pay any attention to their actions.
While soldiers fired tear gas into the protesters, the protesters threw objects into a group of soldiers. Soldiers retreat, as many of them were injured.
Some soldiers are still at Phan Fa Bridge and fire rubber bullets to warn protesters to move out of the area.
3.50: Thai PBS reports that troops are firing tear gas at protesters. A Thai PBS reporter at the scene is apparently affected by tear gas, as she chokes and stops reporting.
Gunshots are also heard as troops fire into the air.
Thai PBS reports that the crackdowns against the red-shirt protesters at Phan Fa have so far wounded 33 people.
4.00: Thai PBS reports that protesters are fighting troops at Makkhawan Bridge. Protesters armed with sharpened bamboo sticks surge at the troops while the sound of gunshots continues. Thai PBS says troops fired rubber bullets at the protesters.
4.12: Protesters cheer as troops step back from the confrontation line at Makkhawan Bridge.
Protesters reclaim their rally area from the troops and push them back across the bridge.
4.18: Thai PBS reports that troops are retreating from Makkhawan Bridge to the area in front of Kurusapa Hall.
The station says the wind blew the tear gas back on the troops, causing them to be unable to defend their position at the bridge.
5.20: Bullets of an M16 assault rifle are found in the area near the Old Siam mall, which shuts down later.
5.21: Colonel Sansern Kaewkamnerd, spokesman of the Emergency Operations Command, confirms that Deputy Prime Minister Suthep Thaugsuban ordered the crackdowns on protesters.
The crackdown began at the First Army Area headquarters and continued to the Phan Fa rally site.
Sansern says 234 companies were mobilised to carry out the operation to break up the demonstration.
The crackdown was necessary, as protesters would not obey the emergency decree, which prohibits demonstrations, he says.
The dispersal of the demonstrators would be completed before night falls, he says.
5.30: About 1,000 troops march from Bovornnivate Temple to the Khok Wua intersection to push protesters back.
5.55: At Phan Fa Bridge, tear-gas canisters are thrown into a group of red shirts sitting in front of the stage, dispersing them.
Reporters also suffer tear-gas irritations. Protesters don masks to protect themselves.
6.00: Protesters shoot tear gas at soldiers. Soldiers play a song called "Rak Khan Wai Terd" (Love Each Other) and tell protesters to go back home.
6.22: Protesters try to fire rockets into the air after seeing a helicopter flying near the demonstration site.
6.51: Soldiers settle in at the Democracy Monument. They play another song, "Poh Luang Khong Roa" (Our Beloved Father), while many protesters express anger at the troops after hearing that many of their numbers were injured.
6.48: Troops keep people out of the Khok Wua intersection on Rajdamnoen Avenue and prepare tear gas and rubber bullets.
6.50: Protesters begin throwing objects, including tear-gas canisters, at advancing troops.
7.00: Troops confront protesters at the middle of Soi Khok Wua.
7.45: Troops shoot rubber bullets into the air as a warning.
8.00: A bomb is hurled into soldiers at the Khok Wua intersection, causing several injuries.
Gunshots and four more explosions are heard.
8-8.15: Grenades are fired into Government House, causing some damage.
9: Protest co-leader Natthawut Saikua offers a ceasefire, saying soldiers should stop shooting before the protesters disperse.
9.15: Centre for the Resolution of the Emergency Situation spokesman Colonel Sansern Kaewkamnerd announces in a broadcast that soldiers would keep their distance from the protesters after both sides stop firing.
9.40: Red-shirt leaders dismiss the possibility of talks with the government, branding Prime Minister Abhisit Vejjajiva a "tyrant".
11: There are 12 reported deaths from the evening's violence - nine protesters, two soldiers and one foreign photographer - and 520 injuries.