Chad's president has ordered the military to retaliate against future attacks from Sudan following a drone attack that killed at least 17 people and injured several other people attending a funeral.

Wearing military uniform, President Idris Mahamat Déby convened an emergency security meeting on Wednesday evening, where he ordered the military to be on high alert. He also ordered a "total closure" of the border with Sudan.

He described the attack targeting the border town of Tiné as "outrageous and a blatant aggression" against Chad's territorial integrity.

He said that it had happened despite warnings to the two sides battling each other in Sudan and a previous closure of the border.

Last month, Chad closed its border with Sudan "until further notice" to stop repeated incursions by Sudanese armed groups.

It however allowed "exceptional exemptions" on humanitarian grounds, with prior authorisation from relevant authorities.

Residents of Tiné said the victims of Wednesday's attack were mourners, with one quoted by the Reuters news agency as saying they had gathered at a house for a funeral ceremony that involved reading the Koran.

The attack drew condemnation from several quarters, including from the National Assembly and MPs from the ruling party.

"The government bows with deep dismay to the memory of the victims and extends its deepest condolences to the bereaved families," a statement by the government spokesman said.

The spokesman said Chad had now "strengthened the posture of its defence and security forces" and was ready to pursue its rights inside Sudanese territory "in strict compliance with the rules of international law".

The paramilitary Rapid Support Forces (RSF), which controls most of the western Darfur region bordering Chad, is suspected of carrying out the attack. It denies any involvement and blames Sudan's army, which has blamed the RSF.

The Sudanese government has often accused Chad of supporting the RSF with weapons and mercenaries, claims which N'Djamena denies.

Sudan has been plagued by a civil war that broke out in April 2023 following a vicious power struggle between its army and the RSF.

The ongoing war has killed hundreds of thousands of people and displaced more than 13 million people, nearly one million of them to Chad, according to the UN.

Chad shares a 1,400km-long (870 miles) border with Sudan that is porous and often difficult to control.

Its order to retaliate against future attacks from Sudan raises fears of a possible escalation of the violence in the region.