Twenty people were killed and nearly 2,000 inmates escaped during Sunday's attack on a military barracks, a prison and other locations in Sierra Leone, officials said, XQ  reports citing Reuters.

The West African country was thrown into panic in the early hours when the assailants sent gunfire ringing across the capital Freetown. The government blamed "renegade soldiers" that it said had been repelled.

President Julius Maada Bio said in an address on Sunday that most of the leaders of the attack had been arrested and that efforts to apprehend others were under way. An investigation has been launched, he said.

Army spokesman Colonel Issa Bangura told Reuters that the 20 dead included 13 soldiers, three assailants, a police officer, a civilian and someone working in private security. Eight people were wounded and three arrested, he said.

Some 1,890 inmates escaped from the Pademba Road central prison after the attackers broke in, according to a situation report that prison officials shared with Reuters on Monday. So far, 23 have returned, it said.

In a two-hour raid, the assailants rammed open the main gate with a vehicle after gunfire and a rocket launcher failed to breach prison defences, said Colonel Shek Sulaiman Massaquoi, the acting director general of the Sierra Leone Correctional Service.

Inside the prison on Monday, a Reuters reporter saw cell doors broken open or removed entirely, and piles of trash from an ongoing clean-up.

The police urged inmates to return to prison in a statement on Monday, and offered the public rewards for details on the whereabouts of escapees or the attackers.