By Tim Cocks and Loucoumane Coulibaly
ABIDJAN (Reuters) - At least 10 people were killed in Ivory Coast on Thursday when a shell exploded in a busy market in an area of the main city Abidjan that supports presidential claimant Alassane Ouattara, two residents said.
Gunfire and explosions were heard in various parts of Abidjan on Thursday and overnight, and the United Nations had earlier confirmed the death toll from Ivory Coast's violence since a disputed mid-December election was now 410.
The world's top cocoa grower has been in turmoil since the election between Ouattara and Laurent Gbagbo, which Ouattara is recognised internationally to have won but which Gbagbo, the incumbent, has refused to concede.
Security in the main commercial city has been rapidly deteriorating since gunmen claiming allegiance to Ouattara took over its northern suburb, prompting pro-Gbagbo forces and allied youth militias to set up roadblocks and kill suspected rebels.
"I went to the market where the rocket landed. There were 12 dead bodies there, and there are many wounded," said witness Sumeiro Vassiriki. Arouna Sylla, another resident, said at least 10 people had been killed and many wounded.
It was not clear who had fired the round.
Witnesses in Siaka Kone market in Marley, part of Abobo district, thought the shell had been fired by forces loyal to Gbagbo who arrived in an armored vehicle.
But a security source denied this, saying they no longer had forces operating in the area.
"There have been no movements or firing from our positions on Abobo today," the security source said. "We're fighting rebels in Williamsville and Yopougon. We don't know what happened (in Abobo) and it isn't our concern. Ask the rebels."
"INCREASE IN VICTIMS"
Fighting has also spread to the west, across a north-south ceasefire line in place since the end of a 2002-3 civil war, increasing fears that an election meant to reunite the country will instead reignite the conflict.
"ONUCI (the U.N. mission) notes an increase in the number of victims after violent clashes in several parts of Abidjan and the interior," U.N. mission spokesman Hamadoun Toure told a news conference at U.N. headquarters in Abidjan.
"Our human rights division (this week) documented 18 new cases of deaths, of which four were women, taking the number of people killed in the country to 410 since mid-December."
Shortly after he spoke, gunfire erupted in a neighborhood nearby, and witnesses reported sporadic automatic gunfire and explosions from heavier weapons in other parts of the city.
A Reuters reporter heard explosions and machinegun fire coming from the direction of Adjame and Williamsville, where security forces have launched a crackdown on suspected rebels, just north of the city center, throughout the afternoon.
"The police are in position and firing in all directions," said Adjame resident Anatole Eba. "There are detonations from heavy weapons. Everyone's staying home."
Rebels controlling the north of Ivory Coast have backed Ouattara in the power struggle and gunmen in the main city Abidjan have expanded their presence from a northern Ouattara bastion closer to the center of town and strongholds of Gbagbo.
Those gunmen advanced across Abidjan on Monday, bringing their fight closer to the city center and presidential palace.
Overnight, a Reuters reporter heard explosions and machinegun fire in the leafy Cocody suburb, where Gbagbo's house is located and broadcasts of state-run RTI television originate.
At least five people were killed by security forces in a crackdown on the Adjame area on Wednesday, witnesses said.
The U.N. spokesman said some children had been killed or mutilated in the violence, and some had suffered "psychological trauma from when their parents were killed before their eyes."
(Additional reporting by Ange Aboa; Editing by David Lewis and Louise Ireland)