The winner of Nigeria's controversial presidential election, Umaru Yar'Adua, has said he wants reconciliation with the country's opposition parties.
Mr Yar'Adua says he is extending "a hand of friendship"
He said those unhappy with the result should seek redress in the courts.
The conduct of last Saturday's poll has been condemned by local and foreign observers who said it was not credible and fell below even regional standards.
The opposition has called for the electoral authority's dismissal and a re-run under an interim government.
Nigerian and international election observers, civil society groups, opposition parties and the Catholic Church have condemned the election as flawed, some calling it "a charade".
They say that in many areas the election was marred by polling stations opening late or not at all, missing ballots and vote-rigging.
Meanwhile, South African President Thabo Mbeki has written to congratulate Mr Yar'Adua on his victory.
It is the first positive message sent to him by a foreign power since his election.
The South Africa government said Mr Mbeki wanted to forge closer working relations between the two countries.
Speaking to the BBC, Mr Yar'Adua said there were lapses and there was need for reform, but he said opposition parties should put their concerns before the courts.
"I have extended a hand of friendship and I will continue to do so and I will continue the effort at reconciliation.
"I have recognised their right to feel aggrieved and disagree with the results. But I have also recognised their rights within the law to take all the necessary actions to seek redress."
The BBC's Alex Last in Lagos says the opposition, publicly at least, are calling for peaceful protest, though often in an indirect way, aware of how easily protest can get out of control and the often severe reaction of the security forces.
At the meeting on Wednesday, they called on Nigerians to join a street march on 1 May - Labour Day - to reject the "sham elections" and call for their cancellation.
It is not clear whether the public will heed their call. Despite genuine anger, there is resignation and not many want to risk everything for an elitist political system, our correspondent says.
Earlier, the powerful Catholic Bishops Conference of Nigeria advised against any mass protests, saying it is best to head for the law courts.
Mr Yar'Adua won by a landslide, gaining 24.6m votes, against 6.6m for his closest challenger, Muhammadu Buhari and 2.6m for vice-president turned opposition candidate Atiku Abubakar.
In addition to his election troubles, Nigeria's Code of Conduct Tribunal is expected to decide whether it could try Mr Abubakar for graft despite his constitutional immunity against criminal prosecution.
Outgoing President Olusegun Obasanjo has defended the organisation of the vote, saying European standards could not be used to judge the situation in a developing country.
The presidential poll was held alongside elections for the National Assembly and Senate.
Nigeria - one of the world's biggest oil producers - is of key strategic interest to both the West and the growing economies of the East.
But despite the country's huge oil wealth, much of the population lives on less than $1 a day.