The oil dispute has led to ethnic clashes in the past.

Since military rule ended, more than 10,000 people are believed to have been killed in ethnic and religious clashes.

But it appears to have been one of the largest and most sustained ethnic clashes in many years.

Between 1972 and 1988, less horrendous ethnic clashes occurred several times.

Attempts to restore democracy the following year led to ethnic clashes.

Ethnic clashes in Burundi dating to 1993 have killed some 250,000 people.

Ethnic clashes are taking place in many American neighborhoods.

Ethnic clashes over the last six months have killed hundreds in this remote region of western Ethiopia.

Information about ethnic clashes, labor strikes, economic problems or political protests often reaches leaders in this way.

The riots have been seen as a forerunner to the 2010 ethnic clashes in the same region.