Heavy shelling and artillery attacks rocked Somalia's restive capital Mogadishu on Monday as the country's embattled parliament comes under attack.

Insurgents fired mortar shells into a compound housing the parliament at a time when the lawmakers gathered for the first session since August, leading to heavy responses from African Union and government troops, who were guarding the premises.

At least 12 people dead and several others injured in the shelling, which targeted mostly on the south and northern Mogadishu, including a local radio station.

"Mortar shells that landed at Radio Voice of Democracy killed two people, including the wife of the radio's director. The injured include the director himself and few others. The shells destroyed the building," said one of the radio's workers.

Several mortar rounds, including some fired from the infamous PM Cannon landed at our neighbourhood. They have caused the death of innocent civilians. Several wounded people were evacuated from one of the house which came under mortar attack," said an eyewitness from Mogadishu's Yaqshid.

Ali Musa, the head of Mogadishu's Emergency Ambulance confirmed the injuries of at least 30 people, who were taken to different hospitals in the capital.

No reports of casualty from the warring sides with both sides pointing accusing fingers on one another for the death and destruction of innocent civilians.