Chad said Thursday its warplanes bombed Boko Haram positions in neighboring Nigeria to avenge twin suicide bombings in the capital this week blamed on the jihadists.

The government also Wednesday announced it was banning the burqa nationwide in a security clampdown following Monday's attacks in N'Djamena that left 33 people dead and more than 100 wounded.

Chad declared three days of national mourning Wednesday for the 33 people killed in twin suicide bombings blamed on Boko Haram on Monday, the first such attacks in the capital N'Djamena.

President Idriss Deby said that the "provisional" death toll had risen from 24 to 33 as he condemned the "macabre and horrible" attacks on the city's police headquarters and police academy.

Scores of police and soldiers patrolled Chad's capital N'Djamena on Tuesday, a day after twin suicide bombings blamed on Boko Haram jihadists killed 24 people and wounded more than 100 in the first such attacks in the city.

The security forces had sealed off the area around the presidential palace, as well as the police headquarters -- which was one of the bombers' targets.