SANAA — A car bomb exploded outside a mosque in Yemen’s war-ravaged capital Sanaa on Wednesday, killing four people and wounding six, health authorities and a security source said.

ISIS claimed responsibility for the attack on the Al Faydh Alhatemy mosque, more commonly known as Burhani, in the eastern Sanaa of Nuqum, describing the bombing as revenge for what it called Ismaili, Shi’a support for Yemen’s dominant Houthi movement.

The blast was the second bombing in Sanaa in three days. A bomb exploded underneath a passenger bus in the southerly Dar Selm area on Sunday, killing three people and wounding five.

No one has claimed responsibility for that blast, but a number of previous such explosions in the city and elsewhere in Yemen have been claimed by Islamic State in recent months.

The Houthis, backed by army units loyal to former president Ali Abdullah Saleh, have been waging a four-month-old war against a Saudi-led Arab coalition that has been seeking to restore to power exiled President Abd-Rabbu Mansour Hadi.

Yemeni forces backed up by Saudi-led coalition air strikes have recaptured positions on the outskirts of Aden used by the Houthi group to fire rockets into the southern port city, local officials said on Thursday.

Human Rights Watch has accused Houthis of indiscriminately shelling Aden.

An attack by an unmanned aircraft on a car in southern Yemen overnight killed four suspected al Qaeda militants, residents and local officials said on Thursday.

Those killed in the strike by a suspected U.S. drone in al-Mahfad in Abyan province included a man described by the residents as a mid-ranking local leader, Ahmed al-Kazimi.