Chad's President Idriss Deby has announced the country's border with the Central African Republic has been closed pending an end to intercommunal violence there that has killed thousands and forced nearly one million people to flee their homes.
Deby said the 1,000km frontier would remain open to Chadian citizens wishing to return home.
"From today our border with this country is tightly sealed," Deby said during a visit on Sunday to the town of Daha, 20km from the border.
"Barring that precise case [Chadians returning home], no one is authorised to cross this border until the crisis in Central African Republic is resolved." His speech was posted on the website of the presidency on Monday.
Thousands of French and African troops have failed to stop the waves of killings that erupted after the predominantly Muslim Seleka rebel movement seized power in the majority-Christian former French colony in March 2013.
Seleka leaders were forced to resign under international pressure but Christian militias known as "anti-balaka" have intensified revenge attacks against Muslims.
Chad, previously at the heart of African efforts to stabilise the neighbouring country, withdrew its forces from the Central African Republic last month.
Chadian troops were accused by many in the Central African Republic of siding with the Seleka rebels.