WASHINGTON (Reuters) - The United States warned its citizens on Tuesday of possible summer terrorist attacks in Europe, saying targets could include the European football championship in France, although a State Department official said there was no specific threat information.

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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 centres and transportation,” the U.S. State Department said in a travel alert that extends through Aug. 31.

The department routinely issues such warnings for individual countries and, at times, for an entire continent even when it does not have specific threat information about particular targets.

The last U.S. warning for Europe was issued on March 22 following the Brussels attacks and was due to expire in late June. State Department spokesman John Kirby said the new warning amounted to an early extension of the previous one.

“We took the opportunity, because it’s the beginning of summer, to make our concerns known,” he told a press briefing, noting several high-profile events in Europe in June and July.

“I’m not aware of any specific, credible, terrorist event around these events or in any particular place in Europe. This was issued ... based on an accumulation of information,” Kirby said.

Responding to the U.S. alert, the head of Italy’s anti-terrorism police unit, Lamberto Giannini, said there were “no specific warnings or particular evidence.” But he told Italian media the situation across Europe “requires maximum attention.”

The British Foreign Office declined to comment but pointed to its own guidance advising of a “high threat” of terrorism in some European countries.

The State Department alert noted France will host the June 10-July 10 UEFA Euro 2106 football championship and 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 was expected to draw up to 2.5 million visitors to Krakow, Poland, from July 26 to 31.