RIYADH, Oct 28: While the United States on Tuesday repeated its advice that private US citizens leave Saudi Arabia, the German embassy in Riyadh has sounded alarm that car bombs could hit commercial centres in the kingdom. The embassy has advised an estimated 1,400 Germans living in the kingdom to avoid visiting commercial centres.

The warning was based on information received by the German embassy on Tuesday, that there was a risk of planned terrorist attacks in the Kingdom.

While terrorists have used explosives targeting Saudi government buildings and residential compounds in the past, car bombs have largely been limited to scattered incidents in Saudi Arabia and to the war in Iraq. But last month, twin car blasts occurred in Jeddah. The bombings caused little damage but were thought to be exercises by militants in training.

Peter Blomeyer, German deputy head of affairs in Riyadh, said on Wednesday that the warning message to Germans was to avoid commercial centres.

He said that the message was not new and it does not come as a shock or surprise to German citizens living and working in the Kingdom. He said that terrorist attacks can happen at any time.

Despite the relative calm and improved security situation in the capital, the Kingdom has been conducting searches across the country for terror suspects responsible for a series of bombings that killed more than 100 people in less than two years. Saudi security forces arrested at least 18 people in the last three days during searches for terror suspects.

Earlier during the year, the United States had twice urged the US citizens to leave Saudi Arabia after attacks on Westerners in the Kingdom and pulled nonessential diplomats from its embassy in Riyadh. A US State Department official said the recommendation to Americans remains the same because the threats persist.

The US embassy in Riyadh estimates that there were between 24,000 and 25,000 Americans in Saudi Arabia, down 20 per cent from 30,000 before departures related to a series of attacks on foreigners in the Kingdom.