MOGADISHU, Somalia — Somalia's government forces have regained control of a high security prison in the capital, Mogadishu, that was attacked Sunday morning by heavily armed suspected Islamic militants in an apparent attempt to free militants held there, police said.

All of the attackers were killed, police said.

Godka Jilacow prison, the scene of the Sunday morning attack, is a key interrogation center for Somalia's intelligence agency and many suspected militants are believed to be held there.

Somali police Capt. Mohamed Hussein said all the attackers were believed killed although he could not say how many. He said he saw at least four dead bodies on the ground outside the prison.

The militants had been "trying to free terrorists held in the prison," he said.

Eyewitnesses said soldiers in speeding pick-up cars rushed to the prison and troops took positions around the facility.

Mohamed Hassan, a resident who lives near the prison in the neighborhood of the presidential palace, said he heard gunfire and explosions as soldiers and militants fought for control of the notorious jail.

Another resident, Mohamed Abdullahi, described a terrifying scene with bullets "flying around."

The attack started when a suicide car bomber detonated an explosives-laden vehicle at the gate of the prison, followed by gunmen who started fighting their way into the prison. Guards fought the attackers who threw grenades to penetrate the prison's defenses, police said.

No group immediately claimed the responsibility for the attack which shattered a period of calm in Mogadishu, which is stabilizing after nearly 20 years of chaotic violence.

The attack on the Mogadishu prison came as government soldiers, backed by African Union troops, launched an assault on militant bases in the southern parts of this Horn of Africa nation.

On Saturday the southern town of Bulomarer, which is about 110 kilometers (70 miles) south of Mogadishu, was seized from militants after hours of fighting.

Al-Shabab, Somalia's al-Qaida-linked rebel group, used Bulomarer to stage deadly attacks across Somalia, including in Mogadishu, say military officials. The military offensive dubbed "Indian Ocean" is planned to oust al-Shabab from one of its last major centers, said the officials. The loss of Bulomarer would leave al-Shabab's current key base of the coastal town of Barawe vulnerable to attacks.