Fighting has escalated in Yemen, with media affiliated to government forces reporting a surge in hostilities with the Houthis on several fronts south of Taiz in southwestern Yemen.

Yemen Today TV reported on Thursday that fighting was taking place on the Al-Aqroudh and Al-Masrakh fronts, as well as in Al-Rahn village in the Sabir al-Mawadim district.

Houthi-affiliated media reported four air strikes against the city of Mocha and its port on the Red Sea, west of Taiz.

Yemeni government forces in Taiz said they repelled attacks on Al-Aqroud, as they tried to break the Houthi siege of the area.

“Our forces have carried out 749 military operations over the past 24 hours, resulting in the death or injury of 239 militants and the destruction of 117 vehicles and armoured vehicles,” Majid al-Nazili, a spokesman for Yemeni government forces, told Al Jazeera.

The Houthis – also known as Ansar Allah, Arabic for Supporters of God – also advanced on Jabal Sabr on Sunday, the strategic mountain overlooking Taiz. It has become the focus of the fighting between the Iran-backed group and forces loyal to Yemen’s internationally recognised government, backed by Saudi Arabia.

Meanwhile, flights have resumed at Aden international airport, the Anadolu news agency reported. Services were suspended on Wednesday after witnesses said a missile had landed on the Al-Nasr Camp, adjacent to the airport, where Yemeni coastguard forces and interior ministry headquarters are located.

A military source told Al Jazeera on Thursday that government forces carried out three air strikes against Houthi military gatherings and vehicles southeast of Taiz, claiming that they targeted the group’s positions and movements on the Al-Aqroud front. This comes as the Houthi group reported more than 100 air strikes targeting the capital city Sanaa, and eight other Yemeni governorates, over the past 24 hours. The surge in fighting across multiple fronts in Yemen has worsened a spiralling humanitarian crisis.

The conflict has forced more than 281,000 people from their homes in Yemen since the beginning of August, according to the United Nations’ humanitarian agency.

The Office for the Coordination of Humanitarian Affairs (OCHA) warned that “time is running out” to deliver aid to the 800,000 people trapped inside the city of Taiz. Humanitarian access has become increasingly difficult over the past three weeks, OCHA said, due to damage to a key road linking Taiz to southern governorates.

Aid supplies now have to pass narrow mountain routes to reach people in need. OCHA called on fighters not to target civilians or aid convoys.

“All parties must respect international humanitarian law and allow safe, sustained and unimpeded humanitarian access so that aid can reach people in need,” it said. The war in Yemen has escalated sharply since the Houthis seized strategic territory from government forces along the Red Sea coast last month, prompting a counteroffensive.

Saudi Arabia has since intensified its strikes on the group. Houthi attacks on Saudi Arabia, which is aligned with Yemen’s government forces, have dealt a blow to the kingdom, the world’s biggest exporter of crude oil, disrupting its businesses, airlines and residents, and damaging its international image.