A unknown number of assailants entered a Bahrain jail and set free some inmates. The prison is known to house many Shiite anti-government activists.
A Bahraini prison was attacked on Sunday by a group of armed men who killed one police officer and allowed a number of inmates to escape.
The Jau prison south of the capital Manama is known to house a number of Shiite prisoners convicted over anti-government protests.
The interior ministry did not comment on the number of attackers or escapees, but announced that police had launched a comprehensive manhunt for the culprits.
"Security agencies are intensifying search and investigation in order to arrest the involved terrorist elements and convicted fugitives," the ministry said in a statement.
Things have been tense in the small but strategically important Gulf state since a series of 2011 Arab Spring pro-democracy protests led by the Shiite majority ended in a violent crackdown on dissent. The ruling Sunni royal family has been accused of being complicit in mass arrests and torture of anyone critical of the government.
Recently, prominent activist Nabeel Rajab has been subjected to a draconian legal nightmare that saw him arrested over Twitter activity, then freed for health reasons, then rearrested, then granted bail only to have his bail revoked hours after the order to free him was issued.
Some 80 civilians and 13 police officers have been killed over the pro-democracy demonstrations in the country. In the wake of the unrest, the royal family has spent millions of dollars on high-ranking public relations firms to revamp the country's image, and the clashes there have received relatively little coverage compared to other Arab Spring uprisings.
es/se (AFP, dpa)