Bangkok will be divided into 14 zones, with at least 100 soldiers deployed in each, bolstering security measures already introduced by police in the city, junta spokesman Sansern Kaewkamnerd said.

The troops "will patrol in the capital and set up checkpoints to guarantee safety. We have stepped up security around Bangkok to ensure the general public will not see any violence," he told AFP.

Thailand's junta chief, General Sonthi Boonyaratglin, ordered the deployment to back up police after an anti-coup protest last Sunday turned violent with more than 100 injured in clashes with police.

The clashes were the first violence since Sonthi toppled the government of prime minister Thaksin Shinawatra in a bloodless coup last September, and came as campaigning got underway for an August 19 referendum to approve an army-backed constitution.

"We are taking tougher legal measures and will take serious legal action against those who violate the law," Sonthi told reporters.

The soldiers will deploy from Saturday through Tuesday, as Thailand observes a long weekend for a Buddhist holiday, but that period could be extended further, said junta spokesman Sansern.

The announcement of the deployment came one day after nine protest leaders were arrested over the clashes.