Lithuania told residents in parts of its central and northern regions to go to shelters on Sunday after an unidentified flying object was detected, prompting a red air alert, the NATO air policing jets being scrambled and Kaunas airport closing for about an hour. Neighbouring Latvia declared a yellow alert in some border areas. The incident comes amid rising tension between Vilnius and Moscow, after Lithuania's parliament gave initial approval to a constitutional amendment lifting its ban on hosting foreign nuclear weapons and NATO bases, a move the Kremlin called a dangerous escalation, and after Lithuania deployed troops along its border with Russia's Kaliningrad exclave (a heavily militarised Russian territory on the Baltic Sea between Lithuania and Poland).