French police patrol in the Gare de Lyon railway station in Paris, October 6 2010, as the French government reinforces 'Vigipirate' public security plan.
The Foreign Ministry has recommended that Bulgarian citizens travelling abroad exercise caution when visiting tourist sites, public places or when travelling by public transport or at mass events, making Bulgaria the latest in a series of countries to issue such warnings.
If the need arises, Bulgarian citizens should contact their nearest diplomatic mission, the Foreign Ministry said.
France has urged citizens travelling to Britain to be "extremely vigilant" amid raised fears of a terror attack there, the BBC said on October 6 2010.
The French government said it was now "highly likely" public transport and tourist sites in the UK would be hit.
The warning followed revelations that a UK terror suspect killed in Pakistan was being groomed to lead a new group in raids on the UK, France and Germany.
Sweden and Japan on October 5 joined the UK and the United States in warning their citizens about possible terrorist attacks in Europe.
The advisories came amid concerns about a possible terror attack by al-Qaeda and other groups, the Voice of America said.
The US and UK issued warnings on October 4 of potential terrorist attacks in Europe.
Washington urged American tourists in Europe to be extra vigilant, while London raised its threat assessment to high for citizens traveling to France and Germany.