Bangkok, Thailand (CNN) -- The Thai capital is on edge Wednesday as police brace for demonstrations over a bill to be presented in parliament that would grant amnesty to people jailed for acts committed during outbursts of political unrest in recent years.
Concerns over the protests have prompted the government to invoke special temporary security measures to prevent demonstrators from entering certain areas of Bangkok, including a zone around the parliament building.
Authorities deployed thousands of police officers equipped with riot gear Wednesday to seal off the areas.
Proposed by a lawmaker from the governing Pheu Thai party, the controversial bill would absolve protesters charged, prosecuted, and convicted for acts against the state since the military coup in September 2006 that brought down former Prime Minister Thaksin Shinawatra.
Most of those convicted are members of the "Red Shirt" movement that supported Thaksin. His sister, Yingluck Shinawatra, is the current prime minister of Thailand.
The groups organizing demonstrations in opposition to the bill say they fear it could set the stage for Thaksin's return from exile.
Thaksin left Thailand in 2008 after he was convicted of conflict of interest charges. He was sentenced in absentia to two years in prison.
Tensions between pro- and anti-Thaksin groups reflect deep divisions in Thai society that erupted into violence in 2010. Protests by the Red Shirts against the government at the time led to a military crackdown during which more than 90 people were killed and hundreds were injured.
Worachai Hema, the lawmaker from Yingluck's party who has proposed the amnesty bill, says it aims to help people who were unfairly prosecuted for expressing their political views.
But human rights organizations have warned that the bill could absolve people who ordered or carried out abuses.
"The ruling party's amnesty bill lets both soldiers and militants responsible for deaths during the 2010 upheaval off the hook," said Brad Adams, Asia director at the advocacy group Human Rights Watch.