ADEN, Yemen (Reuters) - At least eight civilians were killed on Friday in Aden, the temporary seat of Yemen’s internationally-recognized government, amid renewed fighting between southern separatists and government forces, medical sources said.

Separately, a brother of Abdel-Malek al-Houthi, the leader of the Iran-aligned Houthi movement against which the government and separatists are nominally allied, was killed in the capital Sanaa.

The group blamed the killing of Ibrahim Badreddin al-Houthi on “the treacherous hands affiliated with the U.S.-Israeli aggression and its tools”, without providing details.

The escalation in violence complicate U.N. efforts to end the more than four-year-old conflict which has killed tens of thousands of people and pushed the country to the brink of famine.

The Aden clashes began this week after the separatists accused an Islamist party allied to President Abd-Rabbu Mansour Hadi of complicity in an earlier missile attack on a military parade in the southern port city.

The fighting has exposed a rift within the Saudi-led military coalition backing Hadi after the United Arab Emirates scaled down its military presence in areas including Aden amid pressure from Western allies and concerns about Iranian activities around the Gulf of Oman.

Residents said shells landed on civilian homes, with the clashes concentrated in the city’s northern residential areas.

The head of Aden’s health directorate told Reuters that 24 fighters had been killed in the past three days, without specifying which side they belonged to.

Medecins Sans Frontieres (Doctors Without Borders) said it had treated 75 people in a surgical hospital since Thursday night. Most of them were civilians injured by shrapnel during shelling on their houses or stray bullets, the medical charity said.

The interior ministry called on civilians to stay at home and away from flashpoints.

Aid group the Norwegian Refugee Council (NRC) said the clashes have trapped its staff and civilians in their homes for days with dwindling supplies of food and water

“There has been heavy, continuous shelling. We’re still hearing clashes in my neighborhood,” said Amgad, an NRC staff member. “There is no way to get out of the city. Roads are closed and it is not safe. People are scared. We hope this will end soon.”

Prolonged fighting in Aden, a gateway for commercial and humanitarian supplies as well as civilian travel outside of Yemen, could have an impact on the rest of the country, the NRC said.