NATO's Parliamentary Assembly has urged alliance members to stand up to Russia's military assertiveness and to decide to better share the burden of collective defense when they hold a summit in July.

Assembly President, U.S. Congressman Michael R. Turner, on Monday said that "Russia's aggressiveness comes with a price," and urged the member countries to boost defense spending.

Some 250 parliamentarians from 28 NATO member countries and partners have gathered in a three-day session in the Albanian capital, Tirana, under tight security measures.

Terrorism, mass migration, the Ukraine crisis and Western Balkan security have been also debated during the session.