An Islamist commander in Somalia has told the BBC there has been an influx of fighters from overseas joining their battle against the interim government.
The al-Shabab militant leader, who spoke on condition of anonymity, said several hundred foreigners had joined their militia, many from Pakistan.
Meanwhile, at least 30 people have been killed in fighting in the capital, Mogadishu, over the past three days.
Africa Union leaders meeting in Libya are due to discuss Somalia later.
There have been calls for the AU to boost its force of some 4,000 peacekeepers based in Mogadishu.
The BBC's Andrew Harding, in Buale in the south, says an al-Shabab commander confirmed foreign fighters were among his ranks.
The radical al-Shabab Islamists, who are accused of links to al-Qaeda, already control much of the south of the country.
Earlier this week government forces displayed what they said were the bodies of some al-Shabab foreign fighters.
But the insurgents denied that any foreigners had been killed.
Fierce fighting between government forces and militants around Mogadishu continued on Friday for a third day, leaving 30 people dead and 70 wounded.
The fighting started late Wednesday and has continued in residential areas north of the city, witnesses told the BBC
Each side blamed the other for starting the violence.
"We have been attacked and we are defending ourselves and our legal government," said military spokesman Farhan Asanyo on Thursday.
Muse Abdi Arale, of the Hisbul Islam group which fights alongside al-Shabab, said government soldiers attacked them and in response they pushed them back and have taken new areas.
Since 7 May, an alliance of militant Islamist hardliners has been locked in ferocious battles with pro-government forces in Mogadishu.
More than 165,000 people have been forced to flee their homes.