Saudi Arabian security forces arrested a Syrian man accused of plotting attacks and his Filipino accomplice in a raid on an illegal explosives factory in Riyadh, the interior ministry said on Saturday, according to state news agency SPA.

The ministry said those arrested in Wednesday's raid belonged to a "deviant group" - a reference used by Saudi authorities to Al Qaeda or Islamic State, which operates mainly in Iraq and Syria.

It named the Syrian man as Yaser Mohammed Al Barrazi.

Saudi Arabia has this year been grappling with a rising threat from Islamic State, which has called on Saudi Sunnis to carry out attacks inside the kingdom.

Saudi Arabia has arrested hundreds of alleged sympathisers and last week's raids were the second major security operation in the capital in the past month. Security forces captured two suspected militants and seized weapons and a explosive vest in raids on September 15.

This year, Islamic State suicide bombers attacked Shi'ite mosques in the Eastern province and in Kuwait. In August, at least 15 people were killed in an attack on a mosque used by members of a local security force in southwest Saudi Arabia.

Two explosive belts and bomb-making equipment were found in the raid on Wednesday in the Al Fayhaa district of Riyadh, SPA reported.

Another location, which the ministry said was believed to be a staging post for suicide bombers in the Al Jazirah district, was also raided, but nothing was found there.

On Thursday, US Embassy in Riyadh put out a new security warning to US citizens in Saudi Arabia.

"The US Embassy has been made aware of information indicating that there are threats against unspecified compounds in which US citizens reside in the Eastern Province," it said in a statement posted on its website.

The embassy gave no specific details on nature of threat.

Numerous US energy companies operate in the Eastern Province, where most kingdom's oil wealth is located. Most of their foreign staff live in gated communities with high security.-Reuters