At least six people were killed in a US air attack on a convoy of senior al-Shabab leaders in Somalia, with the US saying it was assessing the results to see who died.

The attack on Tuesday targeted vehicles and encampment near Barawe, the armed group's base of operations. The US said the targets were senior commanders of al-Shabab, Ahmed Abdi Godane, also known as Abu Zubeyr.

"US special operations forces using manned and unmanned aircraft destroyed an encampment and a vehicle using several Hellfire missiles and laser-guided munitions," said US military spokesman John Kirby.

Kirby confirmed that the attack was aimed at Godane and that the bombs definitely hit the meeting of al-Shabab chiefs.

The raid reflected a commitment by Washington and its allies "to detect, deter, disrupt and defeat violent extremists who threaten progress in the region, as well as ... threaten to conduct terrorist attacks against innocent people", he said.

US special operations forces [used] several Hellfire missiles and laser-guided munitions. John Kirby, US military spokesman

Al Jazeera's Mohamed Adow, reporting from Mogadishu, said the armed group confirmed they had come under attack.

He said reports suggested that up to 10 missiles had been dropped. However, al-Shabab denied Godane was in the convoy.

The AP news agency reported on Tuesday that six fighters had been killed in the attack.

The attack comes days after African Union troops and government forces launched "Operation Indian Ocean", a major offensive aimed at seizing key ports from the rebels and cutting off key sources of revenue.

The US state department has listed Godane as one of the world's eight top most-wanted men and, if confirmed, his death would mark a serious setback for al-Shabab.

Kirby said Godane was on record on September 2013 as saying his group was responsible for the attack on the Westgate mall in Nairobi, Kenya, where a group of al-Shabab fighters stormed the shopping centre, killing dozens of civilians.