MOGADISHU, March 29 (Reuters) - Fighting erupted across the Somali capital on Thursday when allied Ethiopian and Somali government troops poured onto the streets with tanks in what appeared to be a major push against insurgents, witnesses said.

Breaking a shaky ceasefire in place since the weekend, the Ethiopian and Somali soldiers launched a two-pronged attack from early morning on insurgents' strongholds in the Ramadan area of north Mogadishu and around the main soccer stadium.

Explosions and gunfire rattled around the streets, sending residents running for cover in their homes, witnesses said.

"Early in the morning, the government troops and Ethiopians attacked us at the Ramadan Hotel," one Islamist source involved in the fighting told Reuters by telephone.

Casualty figures were not immediately clear, but there were reports of mass injuries.

"Patients are coming to us by the minute, it is too much," one harried doctor at Madina hospital told Reuters by telephone. "I cannot given you numbers now, we are too busy."

Islamists, ousted from Mogadishu by the Ethiopians and Somali government over the New Year, are blamed for an increasingly bloody insurgency in Mogadishu. Disgruntled clan militia have joined their cause, inhabitants say.

"We are seeing smoke from explosions," said Reuters cameraman Farah Roble, who could not leave his Mogadishu office due to gunfire. "There are helicopters flying around. We haven't seen that before."

The Ethiopians had brokered a truce at the weekend with the city's dominant Hawiye clan after a week that saw at least 20 people killed, soldiers' bodies dragged in streets, and a plane crash probably due to a missile.

That fighting was the worst since the war over the New Year to kick out the Islamists and put President Abdullahi Yusuf's interim government in the capital. The government represents the 14th attempt at restoring central rule in the country since 1991.

The African Union has sent 1,200 troops to help pacify Somalia. But they have also been the target of attacks in the lawless Horn of Africa nation that defied a U.N.-U.S. peacekeeping mission in the early 1990s.