Twenty-nine children who were taking their school exams in the Central African Republic have been killed in a crush after a nearby explosion caused panic, a hospital director told the BBC.

The blast, on the second day of the high-school finals on Wednesday, occurred at an electricity transformer, said Abel Assaye from the Bangui community hospital.

“The noise of the explosion, combined with smoke” caused alarm among the almost 6,000 students sitting the baccalaureate at a school in the capital, Bangui, local radio station Ndeke Luka reported.

President Faustin-Archange Touadéra has declared a period of national mourning.

He also ordered that the more than 280 who were wounded in the crush get free treatment in hospital.

Students from five different schools in the capital had gone to the Lycée Barthélémy Boganda to sit the baccalaureate exam.

The CAR continues to face political instability and security challenges.

Government forces, backed by Russian mercenaries, are battling armed groups threatening to overthrow Touadéra’s administration