Security officials and tribesmen say Saudi-led warplanes bombed Shiite rebels in their northern Yemeni stronghold as fighting raged in an oil-rich eastern province.

The officials say warplanes on Thursday fired at least 20 missiles in Saada, the heartland of the Shiite rebels, known as Houthis. In the southern city of Aden, warplanes bombed Aden University, suspected of being used as a Houthi hideout.

Fierce clashes between pro-government tribal fighters and Houthis were meanwhile underway in the eastern province of Marib, home to much of Yemen's oil industry. Tribesmen say 10 civilians were killed the past 48 hours.

The officials and the tribesmen spoke on condition of anonymity because they were not authorized to brief reporters.