Eight Chadian soldiers were killed in fierce fighting with Boko Haram insurgents at the weekend on islands on Lake Chad, the army said Monday.
"Our forces attacked Boko Haram elements on five islands near Nigeria on June 24 and 25," said Chad army spokesman Colonel Azem, indicating eight soldiers had died and another 18 were wounded.
He also claimed troops had killed 162 jihadists from the Nigeria-based group, and destroyed six vehicles along with many of the motorcycles often favoured by Boko Haram fighters in their raids.
Chad is part of a five-nation regional force -- also comprising Nigeria, Cameroon, Niger and Benin -- fighting Boko Haram, which is blamed for killing at least 20,000 people and leaving another 2.6 million homeless.
Chad's President Idriss Deby threatened on Sunday to pull the country's troops out of peacekeeping operations in Africa because of a lack of foreign financial support.
Chad has contributed the third-largest contingent to MINUSMA, the UN peacekeeping mission deployed in Mali in response to Islamist insurgency, with 1,390 soldiers.
Deby indicated that N'Djamena lacks help to pay for its 2,000 men in the Joint Task Force battling Boko Haram, which emerged in northeastern Nigeria in 2009 and has in recent years attacked across borders.
"We have not at all been supported on the financial, economic side," he said in an interview with several French media.
"If nothing is done, if that goes on, Chad will be obliged to withdraw," he added. "We can't keep being everywhere -- in Niger, in Cameroon and in Mali. All that is excessively expensive."
Chad's army is one of the most battle-hardened in the region, but the country faces a major economic crisis made worse by low oil prices, its main source of revenue.
There have been frequent clashes on the many small islands of Lake Chad since the Boko Haram conflict began in 2009. The lake borders four countries on the edge of the Sahara: Chad, Cameroon, Niger and Nigeria.