The Malawi Electoral Commission has declared ruling party candidate Bingu wa Mutharika the winner of Thursday's presidential election. But the opposition is crying foul and planning to challenge the results.

The Electoral Commission says Bingu wa Mutharika of the ruling UDF party won the election with slightly more than one-third of the votes cast. The commission says John Tembo of the Malawi Congress Party came in second, with Gwanda Chakuamba of the Mgwirizano Coalition a close third in the tight election.

But Mr. Chakuamba unilaterally declared himself the winner Saturday, basing his claim to the presidency on polling figures collected by his party and some independent monitors.

Hundreds of opposition supporters took to the streets of at least three cities on Saturday to protest the delay in releasing the election results.

A spokeswoman for the Mgwirizano Coalition, Kohliwe Mkandawire, says the opposition grouping has rejected the official outcome.

"The results coming from the Malawi Electoral Commission have been cooked for Bingu wa Mutharika," she said. "Gwanda Chakwamba is the clear winner."

Voters in Malawi went to the polls Thursday to choose a new parliament and their third president. Outgoing President Bakili Muluzi is stepping down, as required, after two five-year terms in office.

Mr. Muluzi chose Mr. Mutharika as his successor. Election observers from the European Union said there were serious shortcomings in the election process, including the ruling party's use of state resources in its campaign.

Ms. Mkandawire says the Mgwirizano Coalition is launching an urgent court application to challenge the election results and stop the new president's swearing-in ceremony, scheduled for Monday.

"What we are doing, is we are going to do the legal means. If the courts fail to give us an injunction, there will be mass action," she said. "We have no choice. But we are working hard to avoid mass action, and they should just give us an injunction against the results, against the swearing-in ceremony."

The Malawi Electoral Commission has rejected allegations of vote-rigging, and election officials have appealed for calm.