Terrorists could be planning an attack in Saudi Arabia (search), Britain's government said Monday night.

"We believe that terrorists remain determined to carry out further attacks in Saudi Arabia, and that these may be in the final stages of preparation," the Foreign office said in a travel warning late Monday.

It came after British Airways (searchon Monday canceled Flight BA 263 from London to Riyadh (search), Saudi Arabia, for security reasons.

The Foreign Office had already advised British nationals against all nonessential travel to Saudi Arabia, saying it believed terrorists are determined to carry out further attacks in the country.

Terrorists carried out attacks in Riyadh twice last year.

On Nov. 9, they attacked the Muhayya residential compound in Riyadh, killing 18 people and injuring more than 80.

That followed coordinated bomb attacks against residential compounds in Riyadh on May 12, which killed more than 30 people, including two British nationals.