He also warned Sudan may be heading for a new war if North-South differences on some issues are not settled before a crucial referendum in January.

Amid rising tension, UN envoys urged Sudan to ensure the vote on southern independence is held on time.

Supporters of the two sides clashed in the capital, Khartoum, on Saturday.

A crowd of several thousand northerners demonstrating in favour of unity turned on around 40 southerners who arrived at the rally. The police then joined in, beating southerners who fled the scene, witnesses said.

The referendum is the result of the 2005 Comprehensive Peace Agreement that ended the 21-year civil war between North and South that left up to two million people dead.

UN diplomats fear any delay could cause renewed violence.