Moldova’s foreign ministry has summoned Russian diplomats to protest recent military exercises involving Russian troops in a separatist region of Moldova.

The ministry called the exercises illegal in a statement Thursday, adding that they were “provocative and inadmissible … and undermine the sovereignty and territorial integrity” of Moldova.

Diplomats were called to the ministry late Wednesday after Moldovan separatists and Russian troops staged joint military exercises this week in the breakaway republic of Trans-Dniester.

It was the second time separatists and Russian troops have staged military exercises there this month.

Pro-Russia Trans-Dniester broke away from Moldova in 1990, fearing it would reunite with neighboring Romania. Separatists fought Moldovans in a war in 1992, leaving 1,500 dead.

There are about 1,000 Russian peacekeepers stationed in Trans-Dniester.