The Foreign Office has renewed its warning to avoid non-essential travel to Saudi Arabia following the discovery of a terrorist plot.
Saudi officials blamed the 9 November attack on al-Qaeda
Britons travelling to or choosing to stay in Saudi should make security arrangements, said the advice.
Saudi officials foiled a bomb attack when they discovered a car packed with more than a tonne of explosives earlier this week.
A suicide bombing in Riyadh killed 18 and injured 120 earlier this month.
During the car bomb discovery on 25 November, two suspected militants died in a shoot-out with police.
The Saudi authorities said they believed the attack was timed for the start of the three-day Eid al-Fitr holiday, marking the end of the Muslim holy month of Ramadan.
The Foreign Office said the renewed warnings were also timed as a reminder for people returning to work after the holiday.
It said it continued to believe terrorists are planning further attacks.
In the travel advice issued via its website on Saturday it said: "As the discovery on 25 November of a terrorist plot demonstrates, the terrorist threat across Saudi Arabia remains high.
"If you choose to travel to, or remain in, Saudi Arabia, you should take all necessary steps to protect your safety and should make sure you have confidence in your individual security arrangements."
It continues to urge travellers and residents to maintain a "high level of vigilance" and "adopt a low profile" in the country.
The British Embassy in Riyadh said the Foreign Office advice reflected its assessment of the risks.
The Muhayya residential compound in Western Riyadh - which housed mainly Arab foreign workers, was bombed on 9 November.
More than 30 people, including two British nationals were killed in co-ordinated attacks on residential compounds on 12 May.
Flights from the UK to Saudi Arabia were suspended from 13 August to 6 September this year.