WASHINGTON - THE Somali pirates who took a US merchant captain hostage for five days were heavily armed but inexperienced youths, US Defense Secretary Robert Gates said on Monday, adding that the hijackers were aged 17 to 19.

The pirates who kidnapped Captain Richard Phillips, three of whom were killed by US Navy snipers on Sunday, were 'untrained teenagers with heavy weapons,' Mr Gates told a group of 30 students and faculty members at the Marine Corps War College in Quantico, Virginia.

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.

WASHINGTON - President Barack Obama pledged on Monday that the United States would seek to halt the increasing threat of piracy off the Horn of Africa.

Mr Obama also praised the military's successful efforts to rescue merchant Capt Richard Phillips, who had been held hostage there for several days by pirates.