The United Nations roundly condemned the attack on Thursday on innocent civilians who are increasingly bearing the brunt of a stand-off for the presidency, claimed by both Gbagbo and internationally recognised winner Alassane Ouattara.

"It's quite difficult to avoid the conclusion it is a crime possibly a crime against humanity," said Rupert Colville, spokesman for the UN High Commissioner for Human Rights in Geneva.

Gbagbo's government has denied carrying out the shelling of civilians, denouncing the accusations as a "conspiracy".

Residents on Friday reported more gunfire in Abobo, Abidjan's most populated suburb, where the massacre took place.

"Yesterday at around midnight we heard shooting from heavy weapons.

We got under the bed, on the floor, out of fear of being killed," said one resident.

Several witnesses confirmed the shooting however there was no report on casualties.

In recent days violence has surged in the world's top cocoa producer, raising fears of a growing humanitarian crisis amid the political stand-off as thousands flee the fighting.

Since Monday, fighters backing Ouattara have tried to move south from Abobo, infiltrating neighbouring suburbs and drawing fierce resistance from pro-Gbagbo troops.

UN spokesman Hamadoun Toure said a UN team which visited Abobo on Thursday "could see that the armed forces of president Laurent Gbagbo fired at least six missiles on the market and surrounding areas, causing the death of 25 to 30 people and injuring between 40 and 60."

He said the 10,000 strong UN mission in Ivory Coast, known as UNOCI, "expresses its indignation in the face of such atrocities against innocent civilians. The perpetrators will not go unpunished."

Once seen as the economic miracle of West Africa and a beacon of stability in a troubled region, Ivory Coast was plunged into turmoil after an attempted coup in 2002 against Gbagbo.