Army spokesman General Azem Bermandoa Agouna confirmed that an attack had taken place at Tchoukou Telia, an island 190 kilometres (118 miles) northwest of the capital N'Djamena, but refused to give any toll.

Lake Chad is a vast area of water and marshland bordered by Niger, Nigeria and Cameroon as well as Chad.

Jihadists from Boko Haram and a rival splinter group, the Islamic State West Africa Province, have been using the region for years as a haven from which to attack troops and civilians.

The Chadian authorities tend to call the jihadists "Boko Haram" regardless of their affiliation.

In March 2020, around 100 Chadian troops were killed in an overnight attack on the lake's Bohoma peninsula, prompting an offensive led by Chad's then president, Idriss Deby Itno.

Deby was killed in April 2021 during fighting against rebels in northern Chad and was succeeded by his son, Mahamat Idriss Deby Itno, at the head of a military junta.

Boko Haram launched a revolt in northern Nigeria in 2009 before extending its campaign into neighbouring countries.

According to UN figures, more than 36,000 people, most of them in Nigeria, have died and three million have fled their homes.