Gunmen opened fire on a bus carrying Israelis in the occupied West Bank on Monday, killing at least three people and wounding seven others.

Yemen risks being dragged further into the military escalation in the Middle East and could spiral out of control, the U.N. special envoy for the Arab world’s poorest nation says.

The heads of six U.N. agencies and three international humanitarian organizations issued a joint appeal to Yemen’s Houthi rebels for the immediate release of 17 members of their staff who were recently detained along with many others also being held by the Iranian-backed group.

A U.N. envoy says sporadic armed clashes between Yemen’s Houthi rebels and government forces are straining peace efforts, and the rivals are now also battling over revenue from ports, trade, banking and natural resources.

The U.N. envoy for Yemen has warned that the risk of a return to fighting in the country “is real” and urged warring parties to accept a longer extension of the current cease-fire due to expire next month.