Yemen’s internationally recognised government launched a major military operation on Sunday aimed at retaking territory from Houthi fighters in the western Taiz province, officials said. Council head Rashad al-Alimi announced the operation, describing it as a broad push across multiple fronts. At least 80 combatants have been killed in recent days of fighting around Taiz, with some 20 air strikes reported in the area.

The offensive comes after the Houthis cut the main road between Taiz and the port city of Aden and seized control of the Bab el-Mandeb strait, a vital shipping lane. The UN special envoy for Yemen, Hans Grundberg, said he was alarmed by the escalation and urged restraint. The Houthis have held large parts of Yemen since seizing the capital Sanaa in 2014, and a Saudi-led coalition has backed the government since 2015.

Aid agencies warn that renewed fighting could worsen one of the world’s worst humanitarian crises.