Who are the ONLF?

The ONLF was founded in 1984.

It is fighting for independence from Ethiopia, complaining of discrimination by the central government against the region's Somali-speaking nomads.

Ogaden is the local name for the Somali region.

Some Ogaden residents and Somalis want the region to be part of a "Greater Somalia" - an idea strongly resisted by Ethiopia's government. It is not clear if this is ONLF policy.

The ONLF are backing by Eritrea, which fought a border war with Ethiopia, although this is denied in Asmara.

Have they staged similar attacks before?

The government has accused them of carrying out various bombings both in the Somali region and the capital, Addis Ababa but this is the first attack on a foreign company in the region.

There was a major military operation in the region last year.

The ONLF said it had warned China against looking for oil in the region.

It accuses the Ethiopian army of moving nomads away from their grazing lands in order to prospect for oil.

Communications are extremely difficult with this remote area and accurate information can be difficult to come by.

What is the Somali region like?

This hot, arid region was ceded to Ethiopia by the British in 1954.

Locals complain that they are unable to look after their camels, sheep and goats because of the constant fighting between the ONLF and the Ethiopian army.

Somalia has twice fought wars with Ethiopia to get it back but the Ethiopians have been victorious.

The Islamist group which controlled much of southern Somalia last year said it wanted to bring the region under Somali control.

But the Ethiopians have now helped oust the Islamists and the continued presence of Ethiopian troops in Somalia has exacerbated tensions in the Somali region.

How is China viewed in Africa?

China is generally viewed quite favourably, as it has poured money into Africa in recent years.

Although some see this as exploitation and others complain about bad working conditions in Chinese firms.

Some African governments prefer dealing with China, which does not pay as much attention to human rights as some western ones.