"Security forces have identified a number of individuals involved in terror acts that took place in the kingdom in the past few months," the interior ministry said on Saturday in a statement broadcast on state television and carried by the official SPA news agency.

Meanwhile the US embassy in the Saudi capital Riyadh warned its staff to restrict their movements for fear of further attacks by hardline Islamic armed groups.

The Saudi government published and broadcast photographs of the suspects, who include 23 Saudis, as well as two Moroccans and a Yemeni, urging people to call a toll free telephone number with information on them and promised "generous financial rewards."

The ministry offered one million riyals ($272,000) for information leading to the arrest of any one of the suspects and five million riyals ($1.36 million) for tip-offs leading to the arrest of a group of them.

It said it would give informants seven million riyals ($1.9 million) for information which would prevent a potential attack.

US warning

The announcement came as the US embassy in Riyadh ordered its diplomats and their families to venture out of the city's diplomatic quarter only for "essential business."

"Effective immediately, travel of embassy personnel and dependents off the Riyadh Diplomatic Quarter is restricted to essential business only," it said in a statement.

"Security forces have identified a number of individuals involved in terror acts that took place in the kingdom in the past few months"

Saudi interior ministry statement

An embassy spokesperson refused to say if the order was related to fresh information about the threat of attacks in the kingdom, saying that similar measures are taken from "time to time" at US embassies all over the world with regards to US staff and that policy requires US nationals be informed of such changes.

But the embassy's website message urged all US citizens in the kingdom, who number about 35,000, to be vigilant, saying they should avoid "places and areas, where Westerners are known to congregate, including residential compounds."

High alert

Saudi security forces have been on heightened alert since the 12 May and 8 November attacks on residential compounds in Riyadh which killed a total of 52 people.

A Saudi security official said on Wednesday that security forces captured a suspected perpetrator of the 8 November attack on the Al-Muhaya residential compound that killed 17 people.

The al-Qaida terror network purportedly claimed responsibility for the al-Muhaya attack in an e-mail received by al-Majalla, a Saudi magazine based in London, and warned of more to come.

The security forces have been hunting suspected anti-regime elements for several months, resulting in hundreds of arrests as well as multiple armed clashes, in some cases deadly, between suspects and security forces.