The International Medical Corps (IMC) has condemned the killing of one of its staff by unknown gunmen in the Somali town of El-Berde, 420km northwest of the capital Mogadishu.

Mohamed Muse Ali, 40, a doctor, and his driver, Lel Idris, were killed on 27 June when two men attacked their vehicle. "International Medical Corps mourns the loss of both victims and condemns the violence that claimed their lives," the medical charity said in a statement.

The agency said it was concerned about the deteriorating security environment in the area and urged the international community to address the situation as a matter of urgency.

"This tragic incident is a reminder of what those of us who work in areas of conflict have long known: while the jobs we do are vital to bring hope to disadvantaged people, those jobs also carry significant personal risk," it said.

Ali had just left work and was on his way home when armed men shot and seriously wounded him, Hassan Moalim Yusuf, the head of the Centre for Peace and Human Rights in Bakol, south-central Somalia, said. He died on the way to hospital and was buried the next day in Hudur, 90km southeast of El-Berde.

The IMC operates a maternal and child health-centre, and provides other basic healthcare and nutrition assistance to victims of severe flooding in El-Berde. "About 20,000 Somalis, mainly women and children, are dependent on our services," the IMC statement said.

Meanwhile, the United Nations High Commissioner for Refugees (UNHCR) said that escalating violence in Mogadishu in June had forced more than 3,500 people to flee in recent weeks.

In a statement, the agency reported that only 123,000 of the estimated 401,000 civilians who fled the heavy fighting that raged in Mogadishu between February and May had returned to the capital.