Thailand's senate has unanimously rejected a contentious political amnesty bill, the deputy speaker said, as tens of thousands of anti-government protesters massed on Bangkok's streets.

"This house rejects this bill for consideration," Surachai Lengboonlertcha  said, adding all of the 141 senators present voted against the legislation, which critics say was aimed at helping divisive former premier Thaksin Shinawatra return to Thailand from self-exile.

The decision kicks the bill, which has provoked nearly a fortnight of protest on the capital's streets, back to the lower house, where under pressure Prime Minister Yingluck Shinawatra - Thaksin's sister - has already vowed to kill it. 

Mass protests

The opposition Democrat Party has harnessed the growing anti-government sentiment.
Thousands demonstrated against the bill in Bangkok on Sunday

It was holding an anti-amnesty rally on Monday evening - before the expected vote by the senate - which it said could draw tens of thousands to the city's political centre, heightening fears of clashes with police.

A Democrat lawmaker Akanat Promphan said the protesters would give the government a "deadline" of 6pm (11:00GMT) to kill the bill before taking further - as yet unspecified - actions.

Thousands of police were deployed across Bangkok to keep the peace, including nearly 7,000 officers around the parliament and the prime minister's office.

Since it was passed by the lower house on November 1, the bill has set off daily demonstrations and raised fears of reviving political turmoil that has convulsed the country since Thaksin was toppled by a coup in 2006.

Opponents of the amnesty say the legislation is intended to whitewash Thaksin's alleged crimes and allow him to return to Thailand without going to jail.

Thaksin fled into exile to avoid serving a two-year prison term for corruption.

Source: Agencies