Lithuania's two border crossings with Belarus, at Medininkai and Šalčininkai, were both closed for several hours as a result of the balloon incidents.
Lithuania's Prime Minister Inga Ruginienė said on Monday that her country has drawn up plans to close its border crossings with Belarus indefinitely, after flights at the capital's airport were repeatedly disrupted by suspected sightings of balloons used to smuggle in cigarettes.
Lithuania's National Security Commission met after balloon sightings prompted the suspension of air traffic at Vilnius Airport on three successive evenings on Friday, Saturday and Sunday causing cancellations, diversions and delays.
The airport at Kaunas, which is farther from the Belarusian border, was also affected on the same day.
Lithuania's two border crossings with Belarus, at Medininkai and Šalčininkai, were both closed for several hours following each balloon incident.
The country's border guard service decided overnight on Sunday to close the border for 24 hours, the BNS news agency reported.
Ruginienė said the restrictions will be extended until Wednesday, when her cabinet is expected to decide whether to prolong the closure indefinitely, BNS reported.
Ruginienė said on Monday that the government has already drawn up a draft decision to indefinitely shut the border, with exemptions for diplomats and diplomatic mail.
Lithuanian and other European Union citizens would also still be allowed to enter from Belarus.
Lithuania, an EU and NATO member, is located on the Western alliance’s eastern flank, and it borders the Russian exclave of Kaliningrad as well as Moscow-allied Belarus.
Belarusian opposition leader Sviatlana Tsikhanouskaya, who lives in exile in Lithuania, said that the balloon incidents were "yet another sign that the regime is using cigarette smuggling as a tool of hybrid aggression against Europe."
"The closure of border crossings is a logical step to protect security," she said.
"We support Lithuania and its partners in strengthening sanctions against producers, transporters and organisers of cigarette smuggling."