ADDIS ABABA (Reuters) – The United Nations has suspended food distribution in Ethiopia’s drought-stricken Somali Region after gunmen killed one UN worker and injured another in an ambush on a U.N. convoy last week.

The ethnic Somali province, more commonly known as the Ogaden, is home to a low-key insurgency led by the Ogaden National Liberation Front (ONLF), which has fought for independence since 1984.

On Monday the ONLF accused government troops of killing 100 civilians, including the local U.N. worker, in a five-day operation in the region. The government accuses the rebels of carrying out the attack.

“All operations are frozen at the moment,” Judith Schuler, a WFP spokeswoman in Addis Ababa, told Reuters. “We are constantly re-evaluating the situation in order to restore our operations.”

The U.N. World Food Programme (WFP) says two members of the group are still missing after last Friday’s attack.

The region is also facing a drought-induced food crisis. The United Nations last month appealed for $75 million in food and other aid for two million people in Ethiopia’s southern regions.

The ONLF said the ambush on the U.N. convoy was an attempt to “silence” its employees who had witnessed the operations.

Government spokesman Shimelis Kemal dismissed the claim.

“What happened was that ONLF fighters attacked three WFP trucks transporting food in the region. They have also taken hostages,” he told Reuters.

“Local security officials have captured several suspected culprits and an investigation is still ongoing to recover the hostages,” Shimelis said.

Journalists and aid groups cannot move unhindered in the area, making the allegations very difficult to verify.

Ethiopian forces waged an offensive against the rebels in late 2007 after the ONLF attacked a Chinese-run oil facility, killing 74 people. Analysts say the rebels were weakened but are still able to launch hit-and-run attacks.

Ethiopia says the Ogaden basin may contain 4 trillion cubic feet of gas and major oil deposits.