Somali insurgents fired mortars at Mogadishu's main airport on Thursday just after President Abdullahi Yusuf took off, in the latest of an upsurge of attacks since a peace deal was signed, officials said.

"The president's plane had taken off for Addis Ababa five minutes before insurgents began shelling the airport," a presidential aide told Reuters.

Islamist-led insurgents have stepped up their Iraq-style campaign against the Somali government, and its Ethiopian military allies, since some opposition figures signed a U.N.-brokered peace pact with the government on Monday.

The agreement has had no impact on the ground.

Officials for an African Union peacekeeping force in Mogadishu, which guards the airport, confirmed Thursday's attack, but could not give details.

Earlier this month, Yusuf also escaped unharmed after a barrage of mortars hit the airport runway where a plane carrying him to Djibouti for the peace talks was parked.

Mortars also rocked residential neighbourhoods of south Mogadishu on Thursday. "One mortar round blasted in our neighbourhood, seriously wounding five people including two children," resident Amina Ali, told Reuters.