Militants fought running battles with soldiers as concerned crowds looked on
Pro-government forces in Somalia have launched a major attack against Islamist militants controlling parts of the capital, Mogadishu.
The forces said they had made some progress during fierce clashes - a claim denied by the opposition leader.
At least 36 people were killed and some 180 wounded, medical sources say.
Supporters of the transitional government - which is recognised by the UN - lost control of about one-third of the city to the militants last week.
Ten days of fierce clashes between the pro-government forces and militant Islamic groups - al-Shabab and Hisbul-Islam - have left more than 100 people dead and displaced about 50,000 civilians.
The death toll from Friday's fighting could be as high as 45, Reuters news agency reported.
The BBC's Mohamed Olad Hassan in Mogadishu says most of the fighting is focusing on one of the city's main routes, Wadnaha Road.
"This is a large military offensive against violent people," military spokesman Farhan Mahdi Mohamed told AFP news agency.
"The government will sweep them out of the capital and the fighting will continue until that happens."
The pro-government forces said later on Friday they had made some progress against the militants and then retreated for strategic reasons.
But opposition leader Sheikh Hassan Dahir Aweys said his fighters had been holding ground after repelling the attack.
African Union peacekeepers based in the capital to support the fragile administration are not involved in the attack, our correspondent says.
The 4,300-strong force does not have a mandate to pursue the insurgents.
A moderate Islamist President, Sheikh Sharif Sheikh Ahmed, was elected by a unity government in January as part of a UN-backed peace initiative.
But even his introduction of Sharia law to the strongly Muslim country has not appeased the hardline guerrillas, who are accused of links to al-Qaeda.
Somalia has been mired in conflict for 18 years.