The Ukrainian military's chief of staff says Russia left troops behind in Belarus after staging military exercises there, despite Moscow's pledge not to do so, Reuters reports.

Viktor Muzhenko's comments in an interview with the news agency on September 29 could heighten tensions further between Moscow and Kyiv, which have been locked in a standoff over Russia's 2014 seizure of Ukraine's Crimean Peninsula and its backing of separatists in eastern Ukraine.

The claim also contradicts a statement by the Belarusian Defense Ministry, which said that the last train of Russian troops who participated in the Zapad (West) 2017 military drills left Belarus on September 28.

"We had information that they had withdrawn only a few units of the declared 12,500 troops, of which 3,000 were Russians, but there were significantly more of them there," Reuters quoted Muzhenko as saying.

The September 14-20 war games in Belarus and parts of western Russia triggered concerns in neighboring NATO member states already wary of Moscow's intentions after its seizure of Crimea and military interference in eastern Ukraine.

Moscow and Minsk said the maneuvers involved some 12,700 troops in the two countries combined, but Western officials have said the true number may have been around 100,000.

Belarusian President Alyaksandr Lukashenka said on the final day of the exercises that all Russian troops involved in the drills would leave Belarus.

There was no immediate comment from Russia on Muzhenko's claim.

Based on reporting by Reuters and RFE/RL's Belarus Service