President Mahinda Rajapakse's United People's Freedom Alliance was leading in 21 out of 28 polling divisions declared so far following Thursday's parliamentary poll, according to the elections department.
Counting in another 170-plus divisions was continuing Friday and election officials said the ruling party was ahead in most areas, indicating that it could form a government with a comfortable majority.
It was the first parliamentary election since the government defeated Tamil Tiger rebels in May last year, ending a bloody three-decade conflict, and just three months after Rajapakse scored a resounding presidential election victory.
Rajapakse is widely expected to consolidate his power through Thursday's vote for the 225-member parliament, with expectations he is seeking changes to the constitution that could allow him to serve a third term.
"I want a very strong parliament to develop the country," he told reporters as he cast his ballot in a southern constituency where his son Namal