* Blast comes hours before elections
* Dozens wounded in explosion
* Political violence had killed more than 85 since November
(Adds quotes from relatives, colour, previous LAGOS)
By Joe Brock
SULEJA, Nigeria, April 8 (Reuters) - A bomb blast ripped into a Nigerian election office on Friday, killing at least 10 people and wounding a dozen more just hours before a new attempt to hold a delayed ballot.
The explosion, and a political shooting in which four people died, shattered hopes of a smooth start to elections in Africa's most populous nation, holding its parliamentary ballot a week later than planned on Saturday because of logistical chaos.
Emergency workers said at least 10 people were killed in the explosion in Suleja, on the northwestern edge of the capital Abuja. Ambulances ferried dozens of wounded to local hospitals, but there were not enough medics to treat them.
"That is my cousin," said customs officer Zayyed Saidu, holding back tears and pointing to the barely recognisable remains of a corpse at Suleja's General Hospital. The families of the dead and wounded wept and prayed outside.
"Nigeria has become a place where no one is safe. No we can't have elections. If elections should go ahead how will anyone know they are safe?" said Saidu.
Nigeria is due to hold parliamentary elections on Saturday, presidential elections a week later and governorship polls in its 36 states on April 26.
President Goodluck Jonathan, favourite to win the presidential vote, called the blast in Suleja a heinous attack and ordered security agencies to intensify efforts to protect the Independent National Electoral Commission (INEC).
"He also urges all eligible Nigerians to resist all attempts to deter them from participating in the elections through violence... and to put the perpetrators of electoral violence to shame by turning out en masse," a statement said.
There was no immediate claim of responsibility for the bombing. The device exploded as Nigerians queued to check whether they had been picked to work as election officials, a chance to earn a little extra cash.
The run-up to the polls has been marred by isolated bomb attacks on campaign rallies, violence blamed on a radical sect in the remote northeast and sectarian clashes in the centre of a nation roughly split between a Muslim north and Christian south.
Three people were killed and 21 injured by an explosive device thrown from a car at an election rally in Suleja last month.
Before Friday's explosion, Human Rights Watch had estimated that more than 85 people have been killed in political violence linked to party primaries and election campaigns since the start of November.
Violence has broken out on the eve of elections in Nigeria in the past and has often been used to intimidate the local population by making them too fearful to come out and vote.
Gunmen shot dead four people in the northeastern state of Borno, including an official from the ruling People's Democratic Party (PDP), as they prepared to distribute election materials on Friday, police said.
Radical Islamist sect Boko Haram has been blamed for months of targeted killings of police officers and traditional leaders in Borno, but the violence has become increasingly political and many analysts believe the sect's name is being used as a front for political thuggery.
In the northern city of Kaduna, a man suspected of building building bombs to disrupt the elections was killed late on Thursday when a device exploded prematurely, police said. [ID:nLDE7371GB]
There has also been unrest in the restive Niger Delta in the south, Jonathan's home region and the heartland of Africa's biggest oil and gas industry.
Attackers threw dynamite into a guesthouse owned by an opposition candidate in the parliamentary elections in Bayelsa state capital Yenagoa on Tuesday, while the opposition has accused the local government of preparing violence, an allegation it refutes as a smear campaign.
"The administration has been stock-piling arms and ammunition ... The purpose of this orchestrated violence is to subvert the will of the people," the opposition Labour Party said in a statement this week.
The opposition Action Congress of Nigeria has also accused the ruling party of mass arrests -- including of its governorship candidate -- in the southeastern state of Akwa Ibom and of intimidation in Rivers State, also in the Niger Delta. [nLDE7352CG] (For more Reuters Africa coverage and to have your say on the top issues, visit: af.reuters.com/ ) (Additional reporting by Ibrahim Mshelizza in Hawul, Camillus Eboh in Abuja, Sahabi Yahaya in Kaduna, Samuel Tife in Yenagoa, Nick Tattersall in Lagos; Editing by Matthew Tostevin)