The government of Ethiopia is sending a rescue mission to the remote Somali region where seven Chinese oil workers were kidnapped on Tuesday.
China has strongly condemned the separatist rebel attack against its interests in Ethiopia, in which nine Chinese and 65 Ethiopian workers died.
The workers were abducted by the Ogaden National Liberation Front (ONLF) during an attack on a Chinese-owned oil field.
The Ethiopian leader denounced the attack as "cold-blooded murder".
Ethiopia has accused neighbouring Eritrea of sponsoring the ONLF, an ethnic Somali rebel group.
Eritrea has denied the accusation, saying Ethiopia is trying to trigger a war.
Beijing urged the government in Addis Ababa to ensure the safety of Chinese expatriates after the "atrocious" act.
The clashes took place at an oil field in Abole, a small town about 120km (75 miles) from the regional capital, Jijiga.
"It is an outrage," Ethiopian Prime Minster Meles Zenawi said at a news conference.
"I can assure you that those responsible for this act will pay in full for what they did."
The bodies of the nine Chinese oil workers are due back in the Ethiopian capital within hours.
A government official said the bodies of the Ethiopians who were also killed on Tuesday morning will be returned to their families.
The ONLF has been waging a low-level insurgency with the aim of breaking away from Ethiopia.
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
An ONLF spokesman in London, Abdirahman Mahdihe, insisted in a BBC interview that the raid had been a justified reaction to Ethiopian oppression.
"We have warned the Chinese government and the Ethiopian government that... they don't have a right to drill there," Mr Mahdihe told the BBC's Focus on Africa programme.
"Unfortunately nobody heeds our warning and we have to defend our territorial integrity," he said.
The ONLF has in the past made threats against foreign companies working with the Ethiopian government to exploit the region's natural resources.
A Chinese oil worker said about 200 gunmen attacked the field, where the Zhongyuan Petroleum Exploration Bureau is searching for oil.
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, said.
China has been working to increase its influence and investment in Africa in recent years as it looks to secure energy supplies for the future.