WASHINGTON, May 31 (Reuters) - The United States warned its citizens on Tuesday of possible summer terrorist attacks in Europe, saying targets could include the European soccer championship in France, although a U.S. official said there was no specific threat information.
Concern about security in Europe has increased since the Nov. 13 attacks in Paris that left 130 people dead as well as the March 22 attacks in which two suicide bombers struck Brussels airport and a third the city's metro, killing 32.
"We are alerting U.S. citizens to the risk of potential terrorist attacks throughout Europe, targeting major events, tourist sites, restaurants, commercial centers and transportation," the U.S. State Department said in a travel alert expiring Aug. 31.
The department routinely issues such warnings for individual countries and, at times, for an entire continent or the world as a whole even when it does not have specific threat information about particular targets.
The last warning for Europe was issued on March 22 following the Brussels attacks.
A U.S. official who spoke on condition of anonymity said that the department did not have any specific threat information that gave rise to the latest travel alert for Europe.
"The large number of tourists visiting Europe in the summer months will present greater targets for terrorists planning attacks in public locations, especially at large events," the State Department said in Tuesday's travel alert.
Photos of the aftermath of the Paris Attacks last year:
The travel alert said France will host the June 10-July 10 UEFA Euro 2106 soccer championship and noted France had extended its state of emergency, imposed after the Nov. 13 Paris attacks, through July 26 to cover the July 2-24 Tour de France race.
"Euro Cup stadiums, fan zones, and unaffiliated entertainment venues broadcasting the tournaments in France and across Europe represent potential targets for terrorists, as do other large-scale sporting events and public gathering places throughout Europe," the department said.
It also said the Catholic Church's World Youth Day event is expected to draw up to 2.5 million visitors to Krakow, Poland, between July 26 and July 31, saying local infrastructure may be strained by the large number of visitors to Poland.
"Poland will impose border controls at all of its national borders from July 4 to August 2, and visitors to Poland during this period should be prepared to show their passport and undergo stricter security screening throughout Poland," it said.