Saudi police have arrested five suspected insurgents in raids in several localities in the capital and seized large quantities of explosives and money, security officials said. The officials said the five suspects - four Saudis and one foreigner - are believed to be part of a network preparing for a terror attack in Riyadh. "They were apparently preparing for a terrorist attack, probably soon," one official told The Associated Press on Monday on condition of anonymity because he is not authorised to speak to the media. Another official said police seized some 20kg of explosives and one million Saudi riyals ($373,000) in a raid north of Riyadh. He said police believe the suspects were planning to blow up some government installations.The officials said police first arrested a suspect who had been under security surveillance. He later informed on the others in other hideouts in Riyadh. The officials said in at least one raid police exchanged fire with the suspects while they tried to escape their hideout. There was no report of casualties. The officials did not divulge the nationality of the fifth suspect. He was only identified as "a resident", a reference to expatriates living in the kingdom. It was not clear if the suspected insurgents are related to al-Qaida in Saudi Arabia, which has launched a series of bloody attacks in recent years in Saudi Arabia.