Chad imposed a crackdown on illegal firearms on Tuesday as a state of emergency took effect to curb ethnic violence that has killed hundreds of people and forced several thousand from their homes in the south-east.
The UN refugee agency UNHCR said the inter-communal clashes, linked to a spillover of violence from neighbouring Sudan's Darfur region, risked spiralling out of control and it appealed for an international protection force to be deployed.
"UNHCR urges the international community to quickly mobilise a multi-dimensional presence in Chad to help protect hundreds of thousands of Chadian civilians and Sudanese refugees, as well as aid workers trying to help them," it said.
Chad's government imposed a state of emergency from midnight on Monday across large swathes of the central African country, including eastern zones where attacks on villages by armed raiders on horseback this month have killed hundreds.
The measures gave regional governors wide-ranging powers to ensure security, including a ban on unauthorised firearms. Chad shares with Sudan a warrior tradition and a history of violent clan warfare where the bearing of arms is common.
"Those illegally holding weapons of war, whoever they are, must immediately hand them over to the competent authorities. Those refusing will risk exemplary punishment," Prime Minister Pascal Yoadimnadji said in an address to the nation.
President Idriss Deby's government, already facing an armed insurgency he accuses neighbouring Sudan of backing, says repeated cross-border raids by Sudanese Arab militias known as Janjaweed are turning Chad's Arab and non-Arab communities against each other. Khartoum denies promoting the violence.
"These intercommunal clashes, whose victims run into the hundreds, exceed all proportions and throw into peril national cohesion ... Entire towns have been burnt and livestock decimated," Yoadimnadji said.
The attacks mirror the pattern of violence in neighbouring Darfur in western Sudan where since 2003 Arab militia allied to government troops have targeted non-Arab tribes in their campaign against armed rebels. "We fear the inter-communal hostilities are spiralling out of control and could threaten the entire south-eastern region of Chad," UNHCR said.
It said that since November 4, at least 20 villages south of the eastern town of Goz Beida had been attacked by raiders, who were almost always identified by their victims as Arabs and were often long-standing neighbours.
"They are often well-armed, particularly with Kalashnikovs; on horseback, camelback or in trucks; sometimes in military attire, sometimes in civilian attire," UNHCR said.
Since November 7, some 5,000 newly displaced Chadians had converged on a site for internally displaced people in Habile, 45 km (28 miles) south-east of Goz Beida. This brought to around 68,000 the number of Chadians displaced by violence in the east over the year. More than 200,000 Sudanese refugees from Darfur also shelter in Chad.
Chad and Sudan's people are linked and divided by a complex array of ethnic, political and cultural loyalties that often cross national boundaries left over from the colonial period. Chad and its southern neighbour Central African Republic, which has also fallen victim to the violence from Darfur, have called for the deployment of international peacekeepers. But Sudan has resisted international pressure to allow a stretched African peacekeeping force in Darfur to be put under a robust UN mandate.