Its statement came as Gbagbo’s rival Alassane Ouattara scolded the mission for not doing enough to protect civilians, saying Gbagbo’s security forces had killed 832 people since a contested November election in the world’s top cocoa grower.
Gbagbo’s spokesman was not immediately available to comment.
The power struggle between the two has degenerated into armed conflict, with gun battles and heavy weapons fire in the main city Abidjan and the west, across a north-south ceasefire line in place since the end of the last civil war in 2003.
The U.N. mission said Gbagbo’s men were repairing an MI-24 attack helicopter and readying BM21 multiple rocket launchers.
“ONUCI (the U.N. mission) is closely monitoring these heavy weapons which pose a grave threat to the civilian population. The mission strongly warns this camp that it will not tolerate any attempt to use these weapons and will take action against this in keeping with its mandate,” the statement said.
The mission did not say what action. U.N. military spokesman Rais Chakib declined to give any details on what they would do.
At least 25 people were killed and more than 60 wounded when pro-Gbagbo forces fired a series of mortar rounds into Abidjan’s northern Abobo district last Thursday, including one that exploded in a busy marketplace, the U.N. mission has said.
Gbagbo’s camp has denied being behind the attack.
Ouattara’s camp said on Monday the mission was not doing enough to protect civilians, saying 832 had been killed by being fired on, 1,808 wounded, 876 arrested and 100 were missing.
The mission has a mandate to use lethal force to protect itself or the civilian population, but diplomats are concerned it is too reluctant to use it, for fear of clashes with pro-Gbagbo forces they say are doing much of the killing.
Ouattara’s forces have also been accused of killing some civilians, as well as executing pro-Gbagbo soldiers.
“The government regrets that the humanitarian assistance and protection of the population that it requested from ONUCI has not materialised on the ground,” his parallel government operating out of an Abidjan hotel said in a statement.
The U.N. figures for confirmed deaths from both camps since the crisis is around 400 Ivorians. Hundreds of thousands have fled their homes since the disputed poll.
“ONUCI are engaging all they have to protect civilians. They are patrolling day and night, doing all they can with the materials they have,” the U.N.’s Chakib told Reuters by phone.
Thousands of youth supporters of Gbagbo answered a call to join the army this week, adding to fears that the violent power struggle risks sending the country back to civil war.
The U.N. retracted claims Gbabgo was seeking to import more MI-24 attack helicopters from Belarus late last month.