Sri Lanka's President Sirisena dissolve parliamentThe official notification, which took effect at midnight on Friday (17:30 GMT), would trigger a general election on 5 January.
However, it could be challenged in the Supreme Court.
The sacked prime minister's party says the president does not have the power to take such action.
Last month, President Sirisena named former strongman leader Mahinda Rajapaksa as the new prime minister after sacking Prime Minister Ranil Wickremesinghe and his cabinet and suspending parliament.
But Mr Wickremesinghe has refused to leave, saying his sacking was illegitimate.
An MP from Mr Wickremesinghe's United National Party (UNP) said the move to dissolve parliament was "illegal" and said he believed it would be rejected.
"We are requesting the election commission to solve this issue peacefully without creating a bloodbath in the country," Ajith Perera told the news channel.
According to reports, the Sirisena-Rajapaksa camp are calling a snap election because they did not have enough support in parliament for their new government.
The UNP meanwhile would prefer a parliamentary vote to a national election at this time, reports said.
What has led to this?Mr Sirisena, the president, and Mr Wickremesinghe, the sacked prime minister, joined forces in the 2015 election to defeat the then long-time president, Mr Rajapaksa.
But their uneasy coalition has since fractured and Mr Sirisena announced he was sacking the PM and replacing him with Mr Rajapaksa.
The pair had reportedly clashed in cabinet recently over government plans to lease a port to India.