Heavy clashes killed 39 combatants outside Yemen's rebel-held port city of Hodeida today, as a Saudi and UAE-backed offensive to retake the key aid hub entered its second day.

Yemen's Iran-backed Huthi rebels suffered 30 fatalities in the fighting, which took place two kilometres (1.2 miles) from Hodeida airport, south of the city, medical sources told AFP.

Nine pro-government troops were killed in the same area, the medics said. Military sources said the deaths were caused by mines and snipers.

An AFP correspondent behind the government lines in Al Duraihimi witnessed ambulances arriving from the front loaded with dead and wounded.

Saudi-led coalition warplanes and Apache helicopters provided "continuous" air support to pro-government forces, striking Huthi positions, military sources said.

The Huthis have put up a fierce resistance, however, using snipers to slow the assault, the sources added.

The coalition-backed troops have also been slowed by the need for de-mining operations to advance.

The government side sent significant reinforcements to the front on Thursday, according to military sources and the AFP correspondent.