Rebel gunmen have killed at least 74 people in an attack on an oil field in Ethiopia's remote Somali region, the Ethiopian government says.
Sixty-five Ethiopians and nine Chinese oil workers were killed, while seven Chinese were also taken captive in the incident, an official said.
Ethiopian Prime Minister Meles Zenawi called it a cold-blooded "massacre".
A spokesman for a separatist group, the Ogaden National Liberation Front, said it had launched the attack.
The clashes took place at an oil field in Abole, a small town about 120km (75 miles) from the regional capital, Jijiga.
Ethiopia's Prime Minister Meles Zenawi quickly condemned the attack. "Something of a massacre has happened," he said.
"It was a cold-blooded murder, we are pursuing the perpetrators and will see to it that it doesn't happen again."
A Chinese foreign ministry spokesman said: "The Chinese government strongly condemns this atrocious armed attack."
An adviser to the Ethiopian prime minister, Berekat Simon, blamed the ONLF, which he said had the backing of the Eritrean government.
OGADEN NATIONAL LIBERATION FRONT (ONLF)
Want Somali-speaking region to break away from Ethiopia
Founded in 1984
Has been accused of bomb attacks in Somali region and the capital, Addis Ababa
Fought major battles with Ethiopian government in 2006
A spokesman for the ONLF in London, Abdirahman Mahdi, said Ethiopian troops had been forcing nomadic tribes to leave their traditional grazing areas. "Because of that we had to take action," he said.
"We have warned the Chinese government and the Ethiopian government that... they don't have a right to drill there," he told the BBC's Focus on Africa programme.
"Unfortunately nobody heeds our warning and we have to defend our territorial integrity."
He disputed the government's figures, saying seven Chinese were killed and five seized.
The captives were not being treated as hostages and would be handed over to appropriate authorities, he said.
"We will treat humanely all those under our protection."
A Chinese oil worker said about 200 gunmen attacked the oil field.
The workers were employed by the Zhongyuan Petroleum Exploration Bureau, part of China Petroleum and Chemical Corporation, China's Xinhua news agency reported.
Gunmen briefly took control of the field after a 50-minute fire fight with soldiers protecting it, Xu Shuang, a manager for the oil group, told the agency.
In recent years, China has been working to increase its influence and investment in Africa as it looks to secure energy supplies for the future.
The Somali region - known locally as the Ogaden - is known for its often violent clan politics, the BBC's Amber Henshaw reports from Addis Ababa.
The ONLF has in the past made threats against foreign companies working with the Ethiopian government to exploit the region's natural resources.
The ONLF has been waging a low-level insurgency with the aim of breaking away from Ethiopia.
The incident will also step up tensions in the region, which borders Somalia - where there are often clashes between Ethiopian troops and Islamists, our correspondent adds.