About 800 soldiers from Moldova, the United States, Romania, Poland and Georgia began holding military exercises in Moldova on Sunday. The "Joint Effort 2015" exercises are set to run until Saturday at a military base in the former Soviet nation's second-largest city of Balti, at a time of heightened regional tensions and fears of a possible Russian aggression, the Associated Press reported.

Col. Veaceslav Rusu, the coordinator of the exercises, reportedly said that the war games, which are among the largest ever to be staged in the nation, were being held to test coordination among the countries' forces. He added that Moldovan troops had been trained by U.S. forces in advanced communications and control equipment.

Moldova has a quasi-legal pro-Moscow breakaway region known as Transnistria on its border with Ukraine. In May, Ukraine voted to discontinue military cooperation with Russia, ending the transit rights of Russian soldiers looking to go through Ukraine to reach Transnistria, where Russia has stationed about 1,500 troops and conducted military exercises of its own.

In recent months, Transnistrian officials and public figures have warned of a military buildup along their Ukrainian border. Russian media have alleged that Kiev is setting up missile defense systems, troops and artillery along the border. Transnistrian Deputy Foreign Minister Vitaly Ignatyev warned in June that war was imminent.

Earlier this month, Moscow also considered the possibility of issuing Russian passports to residents of Transnistria born after 1991.

Moldova reportedly stepped up its military exercises after conflict broke out in eastern Ukraine when Russia annexed the Crimean Peninsula last year. Moldova also signed a cooperation agreement with the European Union in June that could see the nation become an EU candidate in the near future. In response, Russia blocked trade in Moldovan fruit, vegetables and meat.