VILNIUS — Lithuania shut down its two largest airports and sealed border crossings with Belarus on Friday after a wave of helium balloons entered its airspace for the third time this month, prompting heightened security measures.

Authorities said Vilnius and Kaunas airports were closed for safety reasons until 2 a.m. (2300 GMT), while border crossings with Belarus will remain shut until midday Saturday.

The Lithuanian government accused Belarus of allowing smugglers to use the balloons to transport contraband cigarettes and blamed President Alexander Lukashenko’s administration for failing to stop the activity. Lukashenko is a close ally of Russian President Vladimir Putin.

“The national security commission will meet again next week to assess the influence of decisions already made and what else could be done in the short term to make it painful to the smugglers and to Lukashenko’s regime, which allows them to thrive,” Prime Minister Inga Ruginiene said in a statement.

According to the national crisis management center, “tens of balloons” were detected by radar on Friday.

Vilnius airport was also forced to suspend operations on Tuesday and Oct. 5 when 25 balloons entered Lithuanian airspace. — Agencies