Suspected Muslim militants opened fire on Americans in the Saudi Arabian capital, Riyadh.

Witnesses said the shooting happened outside a residential compound where US citizens live in the south of the city.

A purported al-Qaeda statement posted on an Islamist website claimed responsibility for the shooting.

The incident took place just days after a major al-Qaeda attack in the eastern city of Khobar killed 22 people, mainly foreigners.

In a separate incident, it is reported Saudi forces killed two gunmen after clashes in the Western city of Ta'if.

The Dubai-based Al Arabiya television said the two men were wanted militants, but that they were not linked to the weekend shooting and hostage-taking rampage.

The violence came as Saudi forces continued a large-scale manhunt for three militants who escaped after the Khobar attack on Sunday.