Saudi Arabia had no information about the threat that prompted the US embassy in Riyadh to issue a warning that a terrorist group may be planning to abduct Westerners in the capital, a Saudi government adviser said on Thursday.

'We have had no prior knowledge or warning about the intelligence that the US Embassy is basing its warning on,' the adviser told Reuters, asking not to be named.

The warning, posted on the embassy's website on Wednesday, also advised US citizens living in the kingdom to carry out personal security measures to minimise the risk of abduction.

A US diplomatic source said the warning was based on 'solid information', but that the embassy had no plans to reduce the hours it was open or repatriate any staff or family members.

'An investigation will be launched into the intelligence the Americans are referring to,' said the government adviser. - Reuters