The FCO advice states: "You should avoid the area and follow the instructions of local security authorities."
Hospital chiefs said that one survivor estimated that many as 20 were dead inside the hotel while 10 bodies were found inside the neighbouring Cappuccino Cafe which was also attacked.
Commandos later used explosives to storm the 147-room hotel as other security forces tried to remove casualties.
The local al Qaida affiliate known as AQIM claimed responsibility online, according to the SITE Intelligence Group.
A failed military coup was staged in the largely Muslim country on September 16 and presidential and parliamentary elections which were held on November 29.
The FCO states: "There could be unannounced demonstrations and strikes and the security situation may deteriorate. You should remain vigilant and stay away from large public gatherings. The airport and land borders may be subject to closure at short notice. Monitor local media and check with your airline for more information."
In a message posted in Arabic on the militants' "Muslim Africa" Telegram account, AQIM said fighters "broke into a restaurant of one of the biggest hotels in the capital of Burkina Faso, and are now entrenched and the clashes are continuing with the enemies of the religion".
