Britain's Foreign Office has warned fans traveling to France for the Euro 2016 soccer tournament that its venues are "potential targets for terrorist attacks."
The Foreign Office website, updated on Tuesday, advised fans to be vigilant at all times and follow the advice of French authorities.
"During Euro 2016, stadiums, fan zones, venues broadcasting the tournament and transport hubs and links represent potential targets for terrorist attacks," the notice read.
Prime Minister David Cameron's Downing Street office said the updated warning was not in response to a specific threat and was being issued to provide relevant information for fans.
Meanwhile, Ukraine's state security service said on Monday a French citizen detained in late May on the Ukrainian-Polish border had been planning attacks in France to coincide with the Euro 2016 football championship it is hosting.
On Saturday, the Ukrainian border guard service reported the unnamed 25-year-old had been arrested with an arsenal of weapons and explosives, including rocket launchers and Kalashnikov assault rifles, in his vehicle.
Security Service of Ukraine (SBU) Chief Vasily Gritsak said the man had made contact with armed groups in Ukraine with the aim of buying weapons and explosives.
His intended targets included Jewish and Muslim places of worship and buildings involved with the football tournament, Gritsak said. French government administration buildings, including those dealing with tax collection, were also a target.
The United States on Tuesday warned its citizens of possible attacks in Europe, saying targets could include the UEFA Euro 2106 football championship in France beginning next week.
Last month, Germany's Federal Criminal Police Office (BKA) also said the Euro 2016 could be the target of terrorist attacks in a report leaked to the Bild newspaper.
Security officials in Europe have been on high alert since the November attacks in Paris that killed 130 people, and French and football officials alike have sought to quell concerns that the championship could be marred by violence. France's parliament voted to extend the state of emergency to the end of July to cover the Euro 2016 and Tour de France. The measure boosting security powers was already extended by three months in February until May 26. Because of fear of a heightened threat of terrorism and after several extremists said they wanted to attack the tournament, more security concerns surround the hotly anticipated Euro 2016 tournament.
While struggling with security threats, France has been also hit by nationwide protests and strikes over a bitterly disputed labor law reform. Tourism agencies in the country warned that the number of tourists visiting Paris is decreasing ahead of the Euro 2016 due to the protests and strikes, which are disrupting transportation.