The state-owned air navigation service provider Oro Navigacija (Air Navigation) told BNS on Tuesday that the Russian aircraft had not been given permission "by the Regional Air Traffic Control Center to bypass a zone of dangerous meteorological phenomena by entering Lithuanian airspace over Lithuania's territorial waters".
Meanwhile, the Russian news agency Interfax quoted the Russian Defense Ministry as saying on Monday evening that the crews of the Russian aircraft "sent a voice inquiry" to the air traffic control center in Vilnius "for an emergency diversion towards Lithuania's air frontier in order to bypass the thunderstorm front".
"On receiving an appropriate permission from the Lithuanian side, the planes were diverted for a short time and, having bypassed the dangerous area, immediately returned to the primary route," the Russian ministry said.
According to Oro Navigacija, six Russian IL-76 transport aircraft maintained contact with air traffic controllers and had their onboard transponders on during their flight from mainland Russia to its Baltic Sea exclave of Kaliningrad late on Saturday.
Four of the planes changed their course because of adverse weather conditions and two of them crossed into Lithuanian airspace, the state-owned company said.
The incident occurred over the Curonian Spit at time of heightened tensions in the region over the ongoing Russia-Belarus military exercise Zapad.
Alexander Udaltsov, Russia's ambassador to Lithuania, on Monday was summoned to the Foreign Ministry and was handed a diplomatic note over the airspace violation,