Saudi Arabia said on Wednesday it had arrested an alleged mastermind of the deadly Riyadh suicide bombings along with several other suspects, as newspapers said some of those held belonged to the al-Qaeda network.
The US embassy warned that more terror attacks in the kingdom might be imminent after the three bombing attacks on May 12 at foreigners' housing compounds in the capital Riyadh which killed 34 people, including eight Americans.
"Between yesterday and today, 11 people were arrested in Medina," Saudi Interior Minister Prince Nayef said on Saudi state television. He said those held included three non-Saudi women, believed to be wives of suspects.
A Saudi source earlier told reporters that five suspects were arrested on Tuesday in the Muslim holy city of Medina.
"We believe that one of them is a main mastermind of the [Riyadh] blasts," the source added.
He said he could not confirm newspaper reports that the five were members of Saudi-born Osama bin Laden's al-Qaeda guerrilla group, blamed for the Sept. 11, 2001 attacks on the US.
The daily Okaz reported that the five had been arrested at an Internet cafe and said the alleged mastermind was a Saudi who was among 19 men listed on May 7 as wanted by authorities on terrorism charges after a shoot-out with police in Riyadh.
Another paper, al-Watan, said security forces had confiscated three computers used by the suspects at the cafe.
Al-Watan said those arrested were suspected of belonging to al-Qaeda and were wanted by the security forces. It also said the suspects included the man who orchestrated the attacks.
Saudi and US officials blame al-Qaeda militants for the Riyadh blasts, which were the first to indiscriminately target civilians in the world's biggest oil exporter.
The US ambassador to Riyadh, Robert Jordan, said on Wednesday that Washington believed there was a threat of more attacks in the kingdom, the birthplace of Islam and a US ally.
"We have concerns about further attacks. We are not convinced this threat is over or [that] it is in any way diminished," Jordan told reporters at the US embassy.
"We don't believe that this is a one-time event. The threat level continues to be elevated at this time," he added.
Washington reopened its diplomatic missions in Saudi Arabia on Sunday after a four-day closure prompted by warnings of more attacks. Diplomats said the embassy was sending home around 30 non-essential staff as a precaution.
Prince Nayef said that the 11 arrests brought to 21 the number of people held in connection with the Riyadh blasts. He said six of the nine suicide bombers had been identified and that four of them had been among the 19 listed as wanted on May 7.
American intelligence agents are in Saudi Arabia to assist in the investigation.
The US embassy said the 60 agents would leave the kingdom by the end of the week and be replaced by a smaller team.
"The FBI team is likely to conclude the evidence gathering by the end of this week," Jordan said, adding that the second team would help review the evidence and conduct interrogations. He described Saudi cooperation as "superb."