Voters lined up as polls opened early Thursday, and Rajapaksa himself voted at his home village of Medamulana in southern Sri Lanka.
Rajapaksa is pushing for a two-thirds majority in parliament, which would allow his party to change the constitution. He is expected to do well, riding on his popularity from last year's victory in the quarter-century civil war against Tamil rebels.
More than 7,000 candidates are contesting 225 seats in Parliament, with some 14 million people registered to vote.
Rajapaksa's coalition holds 128 seats in the outgoing 225-member Parliament, and few expect it to face much competition at the polls.
The opposition is in disarray and has fragmented. Its defeated presidential candidate, former army chief Sarath Fonseka who led the military in its victory over the ethnic Tamil rebels, is facing a court martial. He is accused of planning his political career before he gave up his army post and of breaching regulations in purchasing military hardware.
Despite his detention, Fonseka is running for a parliamentary seat in the capital, Colombo.
The opposition accuses Rajapaksa of stifling dissent, encouraging cronyism and corruption and trying to establish up a family dynasty. Two of his brothers and a son are running for parliament and other relatives occupy top government posts.
Jehan Perera, head of the National Peace Council activist group, said voters had two clear choices: “To strengthen the government further to fulfill its promises ... or to check the government that is riding roughshod over all opposition.” For weeks, Rajapaksa's United People's Freedom Alliance coalition and the main opposition United National Front have campaigned enthusiastically, plastering walls with posters, giving books to children and wheelchairs to the elderly and transporting large crowds of supporters to rallies.
“We ask you to give us a strong Parliament, and this is necessary to go for a massive development program,” Prime Minister Ratnasiri Wickramanayake told supporters on the last day of campaigning Monday.
But despite anger over the stagnant economy, there is little enthusiasm among Sri Lankans for the elections, coming just three months after the presidential poll.
A key issue confronting the new government will be how to reconcile with the minority Tamil community following the end of the civil war.
Rajapaksa has yet to follow though on his promise to discuss a power-sharing deal with the Tamils, more than 200,000 of whom remain displaced by the war.
For Tamils the election is an opportunity to choose a new voice for their community. For three decades, the rebels were the dominant voice, killing opponents who questioned them.
The Tamil National Alliance, a rebel proxy party that had 22 seats in the outgoing Parliament, has split in three, with one faction siding with the government, another shedding its demand for an independent Tamil state and a third seeking a Sri Lankan confederation with Sinhalese and Tamil states.
In the predominantly Tamil north, few appear convinced they can change their lives through the ballot box.
“What is the benefit of voting?” asked Sivagnanam Mahendran, a 45-year-old laborer in the northern town of Manippay. “We have voted in the past, nothing happened. All we got were destruction of life, property and displacement.”
