Anti-government protesters shout slogans during an anti-government rally against amnesty bill in Bangkok, Thailand, Oct. 31, 2013. More than 10,000 of protesters of the opposition Democrat Party took part in the rally near Samsen railway station to oppose the amnesty bill being debated in Parliament. (Xinhua/Rachen Sageamsak)

The opposition Thai Democrats issued on Thursday an ultimatum to the ruling Pheu Thai Party to scrap the controversial amnesty bill by Monday.

"By 6 p.m. on Monday, the bill must be rid from parliament. Otherwise, we will do what we have to do," Democrat MP Suthep Thaugsuban, who is leading a street protest on Ratchadamnoen Avenue, announced to demonstrators there. The ultimatum came after the protest against the blanket amnesty bill escalated on Wednesday.

Local reports put the number of demonstrators at Ratchadamnoen Avenue at 20,000, up from about 10,000 the day before, while the Democrat Party claimed there were 50,000.

The government has announced it will not resume efforts to push through the blanket amnesty bill if it is rejected by the Senate.