CAIRO (Reuters) - A grenade exploded on Friday outside a mosque in Yemen's capital Sanaa, controlled by the Iran-allied Houthi group, residents said, as worshippers were leaving after midday prayers.

There were no injuries or casualties, a Reuters witness said. No group claimed responsibility for the explosion under a parked car by the Bilal mosque in western Sanaa.

Islamist militants have exploited Yemen's 16-month civil war between the Houthis and supporters of President Abd-Rabbu Mansour Hadi, who is backed by a Saudi-led Arab coalition, to strike at both sides.

The Houthis have controlled Sanaa since 2014 when they drove Hadi and his government into exile in Saudi Arabia.

Yemeni government forces and allies from the United Arab Emirates control the southern port city of Aden and have pledged to win back control of the capital.

Islamic State said it carried out an attack on a mosque in Sanaa last September that killed 10 worshippers.

(Reporting by Mohammed Ghobari and Khaled Abdullah; Writing by Tom Finn; Editing by Janet Lawrence)