Ukraine's defence minister on Monday hailed what he called a "positive" round of telephone talks with his Belarusian counterpart, aimed at deflating tensions stoked by massive Russian-Belarus military drills.

"We discussed our agenda and determined our future steps. I view this as a positive signal and a first step toward fruitful cooperation," Ukrainian Defence Minister Oleksiy Reznikov said in a statement.

Reznikov said that his counterpart Viktor Khrenin "assured me that there are no threats to Ukraine from Belarus".

They also agreed to send their respective defence attaches to observe each other's military exercises as a gesture of goodwill, the ministry statement said.

The phone call came on the fifth day of joint drills between Russia and Belarus held along Ukraine's northern frontier, the closest point from which any invading force could reach the capital Kyiv.

The massive exercises, involving tanks and missiles, have fed fears that Russia was preparing an assault on Ukraine, which Washington warns could start "any day".