Chad said on Wednesday it had arrested at least five suspects and had banned religious burqas after suicide bombings blamed on the Islamist Boko Haram killed 34 people.

The two simultaneous attacks on Monday were the first of their kind in Chad and appeared to be retaliation by Boko Haram for Chad's leading role in an offensive against the militants.

Chad, a key Western ally in the fight against armed Islamist groups both in the Sahara and Lake Chad area, revised the death toll up to 34 on Wednesday.

More than 100 people were injured in the attacks on a central police station and a police school in the capital.

"There has been progress," said Abderahim Bireme Hamid, minister for the interior and public security. "Several suspects, between 5 and 6, have been arrested."

Chad, a mostly Muslim country, also said it would ban head-to-toe burqas and religious turbans.

"Even the burqas for sale in the markets will be withdrawn," said Prime Minister Kalzeube Pahimi Deubet, who met religious leaders on Wednesday to discuss the measures.

Oil revenues have helped Chad become a military heavyweight and its troops were vital in driving Boko Haram militants from territory in northern Nigeria this year.

Its capital serves as a command centre for a regional anti-Boko Haram taskforce made up of troops from Nigeria, Chad, Niger, Cameroon and Benin as well as for France's 3,000-strong Barkhane mission fighting militancy in the region.

Neighbouring Niger said on Wednesday its security forces arrested a dozen suspected members of a Boko Haram cell that killed a civilian and kidnapped two youths during an attack on a village in the southeastern region of Diffa this week.