RIYADH (Reuters) -Six Saudis and a Yemeni held in Saudi Arabia on security charges have escaped a detention center in the capital Riyadh, state news agency SPA said on Saturday.

“Seven detainees at Malaz prison in Riyadh, held in connection with security cases, were able to leave the detention center,” SPA quoted an Interior Ministry statement as saying.

It did not say when or how they had escaped.

“They were in Malaz prison and under investigation. Somehow they left the prison, they ran away,” an Interior Ministry spokesman told Reuters.

He said the men were not on any lists of suspected militants wanted by authorities and had not taken part in militant attacks or clashes with police.

A government security adviser said the men had no proven links to al Qaeda militants, who are normally held at a high security prison outside Riyadh.

Saudi Arabia has been battling a campaign of violence by militants linked to al Qaeda who want to topple the pro-U.S. monarchy and expel foreigners from the birthplace of Islam.

“Since they violated regulations, their cases will be withdrawn from the investigating committee and public prosecution and their trial procedures will be halted,” the Interior Ministry statement said.

“If they do not return to the detention center, they will not be eligible for the amnesty granted by the king and will become wanted by security forces,” it added.

Last month King Abdullah renewed an amnesty he first offered two years ago to repentant Islamist militants.

The kingdom also said last month that security forces had arrested 42 suspected Islamist militants in raids across the country over the past few months.