Thousands of people marched in Thailand's capital and blocked a major road on Monday to protest an amnesty bill they said is designed to bring former Prime Minister Thaksin Shinawatra back from overseas exile.

More than 1,000 people blew whistles and temporarily halted traffic in Bangkok's financial district of Silom at lunchtime to protest the legislation, which was approved by the lower house of Parliament on Friday.

Several thousand others joined a peaceful march by the opposition Democrat Party in another part of the city. The party had staged a rally that drew thousands of supporters since Thursday.

The bill would grant amnesties to those involved in the sometimes-violent political conflict that has sharply divided the country for almost a decade.

The Democrat Party says the ruling party-proposed legislation is intended to whitewash Thaksin's alleged crimes and allow his return.

"We will keep on fighting against the amnesty bill and pursue those who are corrupt to the fullest, until the bill is doomed and canceled," said Democrat Party lawmaker Suthep Thaugsuban, who led the march.

After being overthrown in a 2006 military coup, Thaksin fled into exile in 2008 to avoid serving a two-year prison sentence on a corruption conviction.

Thaksin, whose sister Yingluck Shinawatra is now prime minister, won large electoral majorities, especially from rural voters who benefited from his populist policies. But he remains highly polarizing seven years after being ousted over allegations of corruption and disrespect for King Bhumibol Adulyadej. Debate over his return arouses fierce passions that sometimes have erupted into violence.

More than 90 people were killed in 2010 during a crackdown by a Democrat-led government on rallies by pro-Thaksin "Red Shirts" in the heart of Bangkok.

The amnesty bill must be approved by the Senate and then be formally endorsed by the king before becoming law. The Democrats say they will also bring the legislation to the Constitutional Court for a ruling on its constitutionality.

The original draft of the bill did not extend amnesty to the leaders of the pro-Thaksin and anti-Thaksin groups, but a House committee in mid-October changed the bill to include them.

Since then, the legislation has been criticized by various opponents, including critics of Thaksin and members of the Red Shirts who are seeking punishment for those involved in the 2010 crackdown.