The Sri Lankan opposition Tuesday launched protests in and outside parliament against proposed constitutional amendments that would boost the powers of the president.

The amendments were formally proposed by the ruling United People's Freedom Alliance (UPFA) party and debated ahead of a vote planned for late Wednesday.

The changes, which were approved by the cabinet last week, would allow among other things President Mahinda Rajapaksa to run for a third term in 2016.

But the government needs 150 votes to pass the amendments in the 225-seat parliament, and the UPFA has 144 seats. The UPFA was said to have canvassed at least 12 opposition members for support.

Members of the opposition United National Party attended parliament dressed in black Tuesday to protest the proposed changes, which they called undemocratic.

The other main opposition party, the Marxist Janatha Vimukthi Peramuna, or People's Liberation Front, was planning to stage a protest on the route to parliament later Tuesday.

Both parties were planning demonstrations across the country for Wednesday.

The proposed amendments to the constitution would allow Rajapaksa, elected to his second term of office in January, to run again when his current five-year mandate expires.

The changes would also move the power to make key government appointments from a 10-member council to the President's Office.