MOSCOW (Reuters) -The Belarusian defence ministry said on Sunday it had summoned Ukraine’s military attaché to protest against what it called repeated violations of Belarus’ airspace by Ukrainian aircraft.

Since last year’s mass protests in which Russia was allied with Belarusian President Alexander Lukashenko and Lukashenko became louder in support of Moscow over Ukraine, relations between the countries have fallen precipitously.

According to a statement from the ministry, Belarus sent the Ukrainian official a letter of protest.

“The military attaché was informed that the Ukrainian side is avoiding a dialogue to resolve disputes … which is very worrying,” the ministry said.

Belarus claimed on Saturday that during maneuvers, a Ukrainian military helicopter flew one kilometer (0.6 miles), into Belarusian territory. The accusation was denied by a spokesperson from the Ukrainian border guard.

On Sunday, the Ukrainian army stated that they had no other comments to make.

A spokesperson stated that “Maybe somebody made a mistake” and was spreading false accusations to manipulate purposes.

Russian President Vladimir Putin and U.S. President Joe Biden are due to hold a video call https://www.reuters.com/world/us/biden-putin-hold-video-call-tuesday-will-discuss-ukraine-2021-12-04 on Tuesday where they will discuss wider tensions in the region.

NATO Allies and Ukraine allege Russia of assembling tens or thousands of troops at Ukraine’s border in preparation for an attack. Russia claims that such a plan is not in place.