Security has been beefed up in the South ahead of today's election re-run in 38 constituencies, following the deadly attacks during last Wednesday's Senate election.

Three people were killed and 31 injured in the southern provinces of Yala and Narathiwat in a series of bombings and shootings at polling stations and on vehicles carrying ballot boxes.

Yala Election Commission (EC) chief Warothai Naewbanta said the violence could affect voter turnout today and he had been pushed to increase security to protect officials.

Armed escorts will accompany all election workers between their homes and polling stations, and routes used to transport ballot boxes will be patrolled. Three helicopters will also be on standby and, to boost morale, all election officials' allowances will be doubled.

Narathiwat election chief Vichien Suthonnont said officials were fearful as a result of last week's violence but no polling station staff had resigned.

He said the numbers of officials would be increased at polling stations in several districts, including Muang, Yi-ngor, Rusoh, Si Sakhon, Bacho, Sungai Kolok and Tak Bai.

Meanwhile, the southern branch of the anti-Thaksin People's Alliance for Democracy (PAD) said it would resort to civil disobedience by sending representatives to rip up their ballot papers in today's second round of voting for the Lower House.

The PAD said the move was retaliation against the alleged abuse of power by the EC, which it accused of being a rubber stamp for the Thaksin regime.

As chaos is expected in some of the 38 southern districts, the EC threatened to have anyone breaking the law arrested.

Dr Kriengsak Liewchanpattana, a PAD leader in Songkhla, vowed to destroy his ballot paper.

The EC is a hazard to the country and we will oppose it with civil disobedience to gain public attention, he said. Kriengsak will publicly rip up his ballot paper at polling station number two. The EC has dropped charges filed by the PAD and the Democrat Party alleging electoral irregularity in the province.

The PAD earlier filed a lawsuit against the EC in the Administrative Court but the case was turned down.

"Only through an act of civil disobedience will the suffering of the people at the hands of the EC be made known. We have no choice but to face the power of the EC and hope to wake up the people," Kriengsak said.

The EC said it was prepared for mobs invading polling booths in Songkhla.

The province's polling chief Pitoon Jae-hae said: "I believe Songkhla people will not tear up ballot papers as they know it's illegal. But those doing so will be charged under the law."

In Phuket, where the anti-Thaksin and anti-EC sentiment is also high, EC officials warned that anyone destroying ballot papers would be arrested.

"It's illegal and police can arrest these people immediately. It doesn't do any good," said Prapa Kayee, the EC's chief in Phuket.

In Satun province, the Democrat Party's former MP Thanin Jai-samut distributed leaflets urging the public to tick the "no vote" box. This would help dismantle the Thaksin regime, the leaflets said.

The EC has run an intense campaign to urge people to vote in the province and expects a 60 per cent turnout.

Democrat Party advisory board chairman Chuan Leekpai accused the EC of failure to perform its duties.

The former prime minister was in Nakhon Sri Thammarat where the party launched a "no vote" campaign.

He said at no point in 70 years of constitutional democracy had there been such "electoral cheating". The EC helps the government, even when the ruling party is in the wrong, he said.