DAKAR: Around 40 soldiers were killed in an attack on a military base in Chad’s Lake region on Sunday, the central African country’s presidency said on Monday. President Mahamat Idriss Deby launched an operation to track down the assailants, the statement said. The presidency did not name the group responsible for the attack. The region is often attacked by the Boko Haram insurgency, which erupted in northeast Nigeria in 2009 and spread to the west of Chad.