Seven al-Shabaab militants have been killed after an attack on a high-security prison in the Somali capital, the government said.

Loud explosions and gunfire were heard Saturday night near the Godka Jilikou prison where al-Shabaab militants are being held.

Al-Shabaab said in a statement that it had freed "all Muslim prisoners" held at the prison and inflicted heavy casualties.

The state-run Sona news agency reported on Sunday that the gunmen had entered the prison wearing military uniforms.

The government did not say how many security personnel were killed, but expressed condolences to the families of the "sacrificed heroes."

Al-Shabaab has also not announced how many of its members have died.

Gudka Jilikou is a prison located near the Somali presidential palace in Mogadishu.

It is run by the Somali National Security and Defense Agency and houses Al-Shabaab fighters and other high-profile prisoners.

The attack was described as a major security breach for Somalia and raised questions about how the militants managed to gain entry into the heavily fortified area of the capital.

Al-Shabaab, which is affiliated with al-Qaeda, has carried out repeated attacks on the Somali government for the past 20 years.