Colombo: Mahinda Rajapaksa forced himself into the UPFA reckoning to contest the parliamentary poll, an action unprecedented for a former president of the country.
Sirisena was not in favour of granting Rajapaksa a party ticket but his party allies have defied his wishes.
Accusing Rajapaksa of alienating Tamil and Muslim minorities from the Sri Lanka Freedom Party (SLFP), Sirisena had last week asked his predecessor not to create divisions in the party.
Sirisena was Rajapaksa's health minister until he came forward as the opposition unity candidate to challenge the then president last year. He then handed Rajapaksa a shock defeat in the polls.
Polling would close at 4 pm (local time) and the first results are to be announced around midnight, officials said.
The 225 MPs are to be elected from 22 electoral districts for a five-year term.
