An escalation in fighting in Yemen’s Hajjah province has raised concerns about medical support for civilians after Doctors Without Borders this week suspended activities in the area over security concerns.

The medical NGO said on Wednesday it was suspending activities at its hospital in Abs district while “negotiating with authorities to ensure the safety and security” of staff and patients.

The announcement came on the same day that a Houthi rebel attack in the province killed at least nine Sudanese soldiers from the Saudi-led coalition supporting the government, according to a defence ministry source.

The Houthi missile attack targeted a military camp near the border with Saudi Arabia, the source told AFP.

Also on Wednesday, Saudi Arabia’s King Salman Humanitarian Aid and Relief Centre said its mobile medical clinics in Hajjah had treated more than 200 people between February 16 and February 22.

The battle over Hajjah has intensified in recent days.

On Tuesday, the coalition said it had launched strikes against 18 Houthi targets in the previous 24 hours, while pro-Houthi social media outlets said the group “successfully” hit coalition targets.

Meanwhile, in the rebel-held capital Sanaa, four Yemeni journalists who have been detained for seven years could be executed “at any moment”, human rights monitor Euromed said.

Euromed called for the “unconditional” release of Tawfiq Al Mansoori, Akram Al Walidy, Abdul Khaleq Omran and Harith Hamid, who are accused of “collaborating” with the Saudi-led coalition.

The four men continue to be jailed and subjected to “physical and psychological torture” in Houthi prisons while serving sentences imposed without any due process, Euromed said.

The rebel group executed nine people in September on charges of collaborating with the coalition.

The Houthis took over the capital in 2014, prompting the Saudi-led coalition to intervene the following year at the request of the government. Seven years of conflict have created the world's worst humanitarian crisis, according to the UN, which estimates that one child dies every 10 minutes.