Somalia's Al-Qaeda linked Shebab insurgents said Tuesday they had fired on two foreign warships that came in close to the key rebel port of Kismayo, the first such reported incident as they face growing military pressure.

"The mujahedeen fighters opened fire and repulsed two military ships that approached the coast of Kismayo, they were coming close to the coast when they were attacked," said Sheikh Hassan Yaqub, a top Shebab official in Kismayo.

"They have sped away from the coastal areas after the shooting and they are not there anymore," Yaqub added, saying the vessels returned fire before heading away.

"Those war vessels also returned fire," he said, adding that a boy had been wounded in a neighbourhood close to the shore, but that no other casualties had been reported.

The nationality of the reported warships is not known, but several foreign navies operate anti-piracy patrols off the coast of the Horn of Africa nation.

Nine warships in a European Union naval force are currently deployed off Somalia by France, Germany, Spain, Portugal, Italy and The Netherlands.

Several other nations, including Russia and China, also provide protection for their vessels as they pass through the busy shipping route through the Gulf of Aden and the Indian Ocean. Kenya's navy operates small vessels offshore from Kismayo.

"There was heavy fire aimed at military ships that came close to Kismayo port, the Shebab fired artillery and anti-aircraft guns at them, but we don't know if there were casualties," said eyewitness Mohamed Isak.

Abdi Yusuf, another resident of the Islamist-held port, said the Shebab had deployed several fighters along the coast.

"They thought the ships were attacking the city, and so they confronted them with heavy fire... I don't know if the ships returned fire," said Yusuf.

Earlier this month the EU naval force launched its first land-based attack in a night time raid on the Somali coastline, destroying several small boats that the force said were part of pirate operations.

However, the force is deployed to tackle piracy and not to attack the Shebab, who are under pressure from regional forces and Somali government troops.

On Friday the Shebab pulled out of Afgoye, one of their last remaining strongholds, ahead of an advancing column of hundreds of African Union and Somali government troops who launched a long-awaited assault on the town.

The loss of Afgoye, which controls key roads some 30 kilometres (18 miles) northwest of the capital Mogadishu, is another major blow for the insurgents who have been on the backfoot for several months, although Shebab fighters said it was a tactical retreat.

The Shebab have come under increasing pressure in recent months from the now 11,000-strong African Union force AMISOM in Mogadishu and from Kenyan and Ethiopian troops, in the south and west of the country respectively, with the Kenyans now incorporated into AMISOM.