BRUSSELS — The European Commission said Tuesday it was closely monitoring reported bomb threats affecting aviation in Europe, but cautioned that it was too early to determine whether the incidents were linked.

"We are closely monitoring the situation and are in contact with the affected Member States," a Commission spokesperson said in an emailed response to Xinhua, adding that the European Union Aviation Safety Agency was also involved.

"Any threats against civilians are unacceptable. Ensuring the safety and security of citizens remains a priority," the spokesperson said.

ALSO READ: Bomb threats target schools, public institutions across Germany

The Commission declined to draw conclusions on possible links between the reported incidents.

"It is too early to draw conclusions on whether the reported incidents are linked. National investigations remain ongoing and fall under the responsibility of the competent authorities," the spokesperson added.

About seven passenger flights bound for Poland, Bulgaria, Italy and Spain received bomb threats on Tuesday, prompting security checks and temporarily disrupting airport operations. No explosive devices were found.