Doctors Without Borders (MSF) said Tuesday that health services in Yemen were "nearing collapse", with pregnant women dying for lack of transport and hospitals under fire from snipers.

Shortages of food, medicine and health workers are acute, said Thierry Goffeau, MSF's coordinator in Yemen's second city of Aden.

"The population is faced with food shortages, the health system is in a state of collapse. I have never seen such a level of violence," he told a press conference in Paris following a 10-week mission to Yemen.

Nearly 4,000 people have died since a coalition of Arab countries led by Saudi Arabia launched air strikes against Huthi rebels who had seized large parts of Yemen and ousted its president, Abedrabbo Mansour Hadi.

Transport has been totally disrupted by the near-daily air raids, meaning that "women needing a Caesarian die because they cannot get to a hospital in time,"  said Laurent Sury, MSF's head of emergencies.

"It is very difficult to get access to the population and for the population to access hospitals as a result of the bombardments and the fighting," he said.

Sury said 20,000 people had been treated for injuries -- nearly half in the nine MSF health centres, Sury said.

The charity's emergency surgery hospital and trauma clinic in the port city of Aden alone "receive nearly 350 new patients per week," he said.

Pro-government forces retook Aden from the rebels last month, bringing an end to air strikes in the city, but Sury said there were still snipers, and hospitals had to set up steel plates to protect their windows.

Many parts of the city have been destroyed and many are without electricity and water, he added, but residents are starting to return.

In a significant move, pro-government forces retook Yemen's biggest airbase from the Iran-backed rebels on Tuesday while hundreds of Gulf Arab troops landed in Aden to bolster the loyalist fightback.