The rebels arrived just before dawn as the Chinese oil workers slept.

The assault lasted less than an hour. But by the time an estimated 200 gunmen left the remote oil installation, 74 people lay dead in the biggest and most bloody attack mounted by Somali separatist rebels in a dusty corner of Ethiopia.

The Ogaden National Liberation Front, a group with links to the ousted Islamic courts in Somalia, later claimed responsibility in a military communiqué sent to The Times. It is fighting for a separate homeland for the Ogaden region’s population of Somali nomads, with the backing of Eritrea.

Last year the group gave warning that it would target foreign oil companies.

Ethiopia watchers said that they were surprised by the scale of the attack and that it was likely to be linked to unrest in Somalia, which has long threatened to drag the Horn of Africa into a regional war. Nine Chinese oil workers and 65 Ethiopians died, according to officials from both countries.

Bereket Simon, spokesman for the Ethiopian Prime Minister, said that the attack was an act of terrorism.

“This is a cowardly act that has been done under the cover of night,” he said by telephone from the Ethiopian capital, Addis Ababa. “They have been planting bombs in many places but this is the first time they have killed so many people in cold blood. We will do whatever it takes to bring the perpetrators to justice.” Mr Simon said that reinforcements had been sent to the oilfield in Abole, about 240 miles (390km) from the state capital, Jijiga.

A Chinese oil worker who witnessed the attack said that about 200 gunmen arrived at 5am. They opened fire on 100 soldiers guarding the site in a battle that lasted almost an hour, said Xu Shuang, acting manager of the oil company involved. He said that the gunmen took control of the oilfield briefly before escaping with another seven hostages.

The workers were employed by the Zhongyuan Petroleum Exploration Bureau, part of China Petroleum and Chemical Corporation, the Chinese Xinhua news agency reported.

A statement released by the Ogaden rebels said that their “Dufaan” commando unit had completely destroyed the oil installation and three units of Ethiopian government forces.

“The ONLF has stated on numerous occasions that we will not allow the mineral resources of our people to be exploited by this regime or any firm that it enters into an illegal contract with so long as the people of Ogaden are denied their rights to self-determina-tion,” the statement said.

The region, which is the size of Britain, is one of the poorest in Ethiopia. Roads are scarce and vast swaths are entirely inaccessible during the rainy season. Barely 15 per cent of children attend schools.

David Shinn, a former US Ambassador to Ethiopia, said that the scale of the attack was unprecedented and could be linked to Addis Ababa’s role in Somalia. “It might indicate growing unrest in the region generally and particularly in Somalia itself, and that might be giving additional support to the ONLF in the Ogaden.”

Last year a United Nations arms-monitoring report revealed that ONLF leaders were frequent visitors to the Somali home of Sheikh Hassan Dahir Aweys, who later rose to power as hardline leader of the Union of Islamic Courts. ONLF members visited his home in central Somalia to collect arms sent from Eritrea, which has a history of supporting Ethiopia’s opponents. Sheikh Aweys is wanted by the US in connection with Islamic terrorism.

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