(CNN) -- At least 33 people have been killed as fighting rages in the volatile Somali capital of Mogadishu, residents and media reports said on Monday.
The scene in Mogadishu included vehicles sprayed with gunfire.
The violence began in the early hours as Islamic insurgents struck African Union bases and pounded a city market with mortar shells.
"I have never seen such a carnage in my life, it was really hell," said Osmanli Ali Kofi, a local cameraman. "I have personally seen 20 dead bodies."
Islamic insurgents attacked two AU army bases, according to a local Shabelle Radio journalist.
AU spokesman, Col. Berigy Bohuko said his forces defended themselves, but there were no AU casualties.
Mogadishu's airport and presidential palace came under mortar fire, and the Bakara market was struck by mortars, residents said. People died at the market and in a house struck by artillery shell.
Somalia has been without an effective central government since 1991, resulting in violence and anarchy.
Islamic militants have been battling Somalia's fragile government and its Ethiopian allies since 2006, when Ethiopian troops ousted the Islamists from Mogadishu and much of the southern part of the country.
Thousands of civilians have died in the fighting and hundreds of thousands more have fled the capital. Watch people surround a bus riddled with bullet holes »
Piracy is also rife off the coast of the Horn of Africa nation.
Fifty-seven ships have been attacked this year, most in the Gulf of Aden, prompting the U.S. Naval Central Command to establish a security corridor patrolled by an international coalition of warships.
The Gulf of Aden, connecting the Red Sea and the Indian Ocean, is one of the world's busiest waterways with about 20,000 ships passing through it annually.
Journalist Mohammed Amiin Adow contributed to this report.