The United Nations says fighting in southern Somalia has forced aid groups to halt operations in a town that is key to the famine relief effort.

The U.N. refugee agency says humanitarian operations have been put on hold in Dobley because of fierce clashes between opposing armed groups.

Spokesman Adrian Edwards said Tuesday the fighting has forced a “significant” number of people to flee Dobley, and said the agency is concerned they will get caught in the violence. The agency says it has received unconfirmed reports of deaths and scores of injuries.

Dobley is a main transit site for Somalis fleeing to the massive Dadaab refugee complex just across the border in Kenya. There is also a temporary shelter in the city for internally displaced Somalis seeking lifesaving food and aid.

Edwards said humanitarian workers have been withdrawn from Dobley until the security situation improves. Operations have also been temporarily suspended in the Kenyan border town of Liboi because of the security threat.

The U.N. agency did not identify the groups that are fighting in Dobley but called for an immediate end to the clashes so that aid operations can resume.

Hundreds of thousands of Somalis have fled to Kenya and Ethiopia this year, trying to escape drought, famine and fighting. Dadaab alone holds more than 450,000 Somali refugees.

Much of the famine-hit southern region in Somalia is held by the al-Qaida-linked militant group al-Shabab. The group has banned most foreign aid groups from operating in areas under its control.