Lithuania has begun enforcing a visa regime with Russia as part of its preparations to join the European Union next year.
By Sarah Rainsford
BBC Moscow correspondent
The EU wanted a tight visa regime to protect its new eastern border.
Russia feared its enclave would be forced into isolation
The move will have a major impact on the lives of at least a million people in the Russian Baltic enclave of Kaliningrad, trapped between Lithuania and Poland.
Residents here can only travel to and from Russia proper with permission from Vilnius.
'Model of co-operation'
Until now travelling between Moscow and Kaliningrad couldn't have been easier.
Russian citizens presented a simple transit paper at the Lithuanian border. Those days have now gone for good and the issue of access to Kaliningrad threatened to turn ugly.
Russia's relations with Europe were at stake.
Russia feared its enclave would be forced into isolation and Moscow dug her heels in.
But after a passionate debate the two sides agreed on a compromise - a new travel document, that's cheap and easy to obtain.
They now hail the agreement as a model of co-operation.
And for those who want to bypass the bureaucracy altogether, Aeroflot has doubled its daily flights, ruling Vilnius out of the equation entirely.
Building on its unexpected success, Moscow now wants to go further.
President Vladimir Putin is pushing for Russians to be granted visa-free travel all over Europe.
But until he can prove Russia's making substantial progress in tackling organised crime and migration, no-one in Europe is taking him seriously.