Saudi-backed Yemeni government forces seized key positions around the Bab el-Mandeb Strait on Monday, according to Reuters, pushing back last month’s advances by the Iran-backed Houthis. The forces took large parts of the Dhubab district, which overlooks the vital waterway, with heavy air support from a Saudi-led coalition.

Yemen’s government said its forces retook the town of Dhubab north of the strait and the nearby towns of Bab and Hadeid. Coalition spokesman Maj. Gen. Turki al-Malki said about 100 fighter jets were supporting the operation and that hundreds of Houthi targets had been destroyed. The Houthis denied the claims, according to reports.

The offensive, dubbed Operation Yemen Dawn, began after President Rashad al-Alimi announced on Sunday that government forces would fight until the country was liberated from the Houthis. Fighting also raged around Taiz, where sources on both sides told AFP that more than 70 people were killed over the previous day.

The Houthis retaliated by claiming missile and drone strikes on Saudi targets, including King Khalid International Airport in Riyadh and an Aramco refinery in Rabigh, Reuters reported. The clashes threaten another major oil route while Iran’s closure of the Hormuz Strait already restricts Gulf energy exports.