Nigeria’s main opposition parties have called for Saturday’s presidential election to be postponed.
In a statement, 18 parties also threatened to boycott the poll unless several of their conditions were met.
Their demands include the annulment of last weekend’s state polls described by the opposition as a “sham”, and the disbanding of the electoral commission.
In a separate development, a curfew continues in the northern city of Kano, after a day of violence by Islamists.
On Tuesday, members of an Islamist group known as the Taleban stormed a police station in Kano, killing at least 13 people.
Police said the militants had come from north-eastern Nigeria to avenge the assassination of a radical Islamic preacher, who was shot dead at a mosque last Friday.
Protest calls
The opposition parties called for a postponement of Saturday’s presidential elections after lengthy talks in the capital, Abuja.
In the statement, they demanded the “total voiding” of the 14 April state elections and the complete disbandment and reconstitution of Nigeria’s National Electoral Commission.
Nigeria’s governing People’s Democratic Party (PDP) has won 26 of the 33 states declared so far.
The opposition parties also urged Nigerians to “protest in a non-violent manner these sham elections so far held, and to resist further elections under the current structure”.
The opposition said the electoral commission was under the control of outgoing President Olusegun Obasanjo.
The opposition coalition includes Vice President Atiku Abubakar and former military head of state Muhammadu Buhari.
They are regarded as the main challengers to Umaru Yar’Adua – the governing party’s presidential candidate.
It is highly unlikely that the government will fulfil the opposition’s demands ahead of Saturday’s polls, the BBC’s Will Ross in Abuja reports.
Apart from attempting to discredit the elections, many observers question what the opposition would achieve by boycotting, our correspondent says.
There has been a worrying spate of violence, including killings, in the run-up to the polls.
Many Nigerians fear further violence ahead of the vote, which should lead to the first handover of power in Africa’s most populous nation from one civilian to another.
President Obasanjo is standing down after two terms in office.