MOGADISHU - SOMALIA'S hardline Shebab Islamists on Monday claimed responsibility for a mortar attack targeting US congressman Donald Payne, who was unharmed, one of the group's officials said.

'We carried out mortar attacks against the enemy of Allah who arrived to spread democracy in Somalia,' Sheikh Husein Ali Fidow told reporters in Mogadishu.

'This government is welcoming America, which is our prime enemy and we will never stop attacking them,' he added.

Mortar shells were fired towards Mogadishu airport as Mr Payne was leaving Somalia after holding talks with President Sharif Sheikh Ahmed and other officials over rampant piracy off the country's coast.

An African Union official told reporters the New Jersey congressman flew out safely.

His visit came the day after US forces shot dead three of four Somali pirates who had been holding an American captain hostage for five days in the Indian Ocean.

In Washington, US State Department spokesman Robert Wood said Mr Payne was provided with a 'very frank and straightforward assessment of the security situation on the ground.'

He however said: 'My understanding is there are no DS (Diplomatic Security) agents protecting him.'

Somalia has been ravaged by violence since the 1991 ouster of president Mohamed Siad Barre.

The unrest has frustrated efforts to establish a central authority.

Ransom-seeking Somali pirates have ramped up attacks against vessels in the Gulf of Aden and the Indian Ocean despite the presence of an international anti-piracy naval force. -- AFP