The public should not panic or spread rumours as security measures are tight, with 24-hour monitoring, General Prayut Chan-ocha, director of National Security Office Region 1 and Army Commander Region 1 said.

"There have been no reports of possible terrorism. However, we have set up a control centre to monitor and prepare for any attack round the clock," he said.

"The military is now preparing special tightened measures for the Bangkok metropolitan area as it is not under martial law. We are working closely with metropolitan police," Prayut said.

Three spots with the tightest security are Sanam Luang, Suvarnabhumi Airport and Buddhamonthon, said Phongsak Semsant, a permanent secretary at the Bangkok Metropolitan Administration.

"During the holiday, the number of passengers will rise on both domestic and international flights, so we have to pay special attention here," he said.

At Sanam Luang, an official venue for the ceremony organised by the government, thousands of Buddhists gathered from early morning until 8pm.

The ceremony was held peacefully.

At Suvarnabhumi Airport fewer entrances are in use with more security officers and random checks of luggage, said the airport's director Sereerat Prasutanont.

A ceremony was attended by many Buddhists in Chiang Mai's Wat Phra Sing.

Apart from normal ceremonial activities, the province introduced the freeing of birds by the Ping River.

The ceremonies in the southern provinces were less enthusiastic with only a limited number of Buddhists in the area.

A service was held briefly at Muang Yala Temple.

"It is due to the southern violence. We decided to restrict the service to before 11am," said Phra Khru Wichiankitikhun Kitiyano of Wachiraprakarn Temple, also in Yala.

Mobile phone signals for all system operators were cut throughout the province of Yala last night, and the wien tien candlelit possession was moved from night-time to 2pm.