Early results from Nigeria's election suggest the majority held by President Goodluck Jonathan's People's Democratic Party in parliament has been cut.
Two newly-formed parties, the Congress for Progressive Change and the Action Congress of Nigeria, appear to have made gains in Saturday's vote.
Despite some violence, observers said it was the best conducted poll since the return to civilian rule in 1999.
Previous elections have been marred by widespread fraud and intimidation.
Officials said steps taken to avoid vote rigging, such as the preparation of a new voter list and very tight security at polling stations, had helped cut down on abuses.
One People's Democratic Party candidate said that the measures to curtail rigging were allowing other parties to make gains.
Reports from Nigeria suggest the Action Congress of Nigeria leading in many races for senate and house seats in the south-west of the country.
The Congress for Progressive Change was said to be doing well in parts of the Nigeria's north.
Several newspapers reported that house of representatives speaker Dimeji Bankole would lose his seat while the daughter of ex-President Olusegun Obasanjo would not be re-elected to the senate. Both are People's Democratic Party stalwarts.
Elections for the presidency and state governorships are to be held on 16 and 26 April respectively.