Thailand tightened security on Sunday after two grenades exploded outside branches of the country's biggest bank in a suspected reaction to a court verdict against deposed premier Thaksin Shinawatra.

The blasts late Saturday targeted branches of Bangkok Bank, causing damage but no casualties, and came just over a week after Thaksin supporters protested at the bank's headquarters over its alleged links to the coup that ousted him.

Prime Minister Abhisit Vejjajiva said he had asked troops to help provide extra security across the country following the attacks, but said he had not enacted harsh security laws as the government had earlier threatened.

"The bomb incidents were expected after the verdict. They are the actions of a small group of people who want to create unrest," Abhisit said in his weekly television broadcast.

Thailand's Supreme Court on Friday confiscated 1.4 billion dollars of Thaksin's fortune for abuse of power while he was in office between 2001 and 2006. He is now living in exile to avoid a two-year jail term for graft.

Abhisit said police and soldiers were monitoring at checkpoints and that the government would install more CCTV cameras.

"Our society is in a challenging situation right now," the premier added.

Military 'conspiracy'

The first blast hit a branch in the Silom business district, shattering windows and doors, while the second caused similar damage and also wrecked telephone booths in Samut Prakarn on the outskirts of the capital, police said.

Another two unexploded grenades were defused at Bangkok Bank branches at around the same time, police spokesman Major General Piya Uthay told AFP .

Thaksin and his supporters, known as the "Red Shirts" because of their signature garb, have vowed to fight back against the court verdict, branding it a conspiracy by Thailand's military, bureaucratic and palace elites.

The Red Shirts have said they will hold a mass rally in Bangkok in mid-March, although they have promised that their campaign against Abhisit's government will be non-violent.

Hundreds of Red Shirts surrounded Bangkok Bank's headquarters in Silom one week before the verdict, forcing it to close for the day.

They said the bank has links to chief royal adviser and former prime minister Prem Tinsulanonda, whom they accuse of masterminding the 2006 coup against Thaksin.

On February 14 police defused a bomb near the Supreme Court while a grenade exploded near government offices. Police have not made any arrests yet in connection with any of the incidents.

Ruling adds 'breathing space'

Thaksin on Saturday rejected calls from the ruling party to leave the political stage, saying he would "not chicken out", and dismissed its claims that a compromise had been struck by returning a portion of his frozen funds.

Analysts said they believed the ruling was a compromise and that it could ease initial tensions, but that it would not solve the simmering conflict between Thaksin's supporters and foes.

"It adds some breathing space to what could have been a volcanic eruption," said Paul Chambers, a senior research fellow in Thai politics at Germany's Heidelberg University.

The Red Shirts, largely from Thaksin's stronghold in the nation's poor north and northeast, loved his populist policies and accuse Abhisit's government of ignoring their plight since he took power in December 2008.

The tycoon's opponents accuse Thaksin of being corrupt, dictatorial and of threatening Thailand's widely revered monarchy.

King Bhumibol Adulyadej, 82, who is regarded as a stabilising figure by many Thais, returned early Sunday to the hospital where he has spent the past five months after a brief outing to his palace for a private function, police said.

- AFP