Washington, Mar 23 (IANS/EFE): The US government alerted its citizens to "potential risks" of travelling to and throughout Europe following a series of attacks at Zaventem airport and a Metro station in Brussels, which killed at least 34 people and injured over 200.

"Terrorist groups continue to plan near-term attacks throughout Europe, targetting sporting events, tourist sites, restaurants and transportation," the State Department said in a statement on Tuesday.

The government, which urges the US citizens to "exercise vigilance when in public places or using mass transportation", stated that the travel alert expires on June 20 without explaining the choice of this date.

"European governments continue to guard against terrorist attacks and conduct raids to disrupt plots," the State Department added in the warning.

"We work closely with our allies and will continue to share information with our European partners that will help identify and counter terrorist threats."

US authorities on Tuesday reinforced security at main airports and subways all over the US after the attacks in Belgium.

The Islamic State (IS) terror group claimed responsibility for the attacks in Belgium.