The leader of Belarus visits a military base where Russian forces are stationed.

President Aleksandr G. Lukashenko of Belarus on Friday visited a military base in his country where Russia and Belarus have been conducting joint exercises, adding to creeping fears that Moscow could use Belarus as a launchpad for a new ground offensive into Ukraine.

Recent interactions between Mr. Lukashenko and President Vladimir V. Putin of Russia, his close ally and benefactor, have amplified concerns that Moscow will try to draw Belarus, Ukraine’s northern neighbor, more directly into the war. Russia used Belarus as a staging ground for the start of its full-scale invasion of Ukraine in February.

Mr. Lukashenko met last week with Mr. Putin at a regional summit in Russia, a week after Mr. Putin made a visit to Belarus. While statements from the Kremlin and from the Belarusian president’s office about the summit did not mention Ukraine, the trip underscored Mr. Lukashenko’s closeness to Mr. Putin.

On Friday, Mr. Lukashenko visited the military base and training area where Russian forces are stationed alongside his country’s troops, speaking to soldiers and receiving updates on how things were going, the Belarusian state media agency, Belta, reported.

“This is important not only for me — this experience is important for Belarus,” Mr. Lukashenko said, according to Belta.

The Belarusian leader also checked “the quality of combat training” of a Belarusian Army unit and spoke with Russian military personnel, the agency reported.

His visit came a day after the Belarusian Defense Ministry said that the buildup of what it calls a “joint regional group of troops” with Russia was continuing, step by step, and that the two countries were planning a joint military aviation exercise.

“Personnel, weapons, military and special hardware of Russia’s armed forces continue arriving in Belarus,” the ministry said in a statement, according to Belta.

Mr. Lukashenko has said that the joint group was necessary to counter “possible aggression” against Belarus by NATO and Ukraine.

Belarus depends on Moscow for fuel and security. And although Mr. Lukashenko has resisted being drawn more centrally into the war, he has come under increasing pressure from Moscow.

The Institute for the Study of War, a Washington-based research group, said in a report last month that while a renewed Russian invasion from Belarus was “unlikely” this winter, the threat of such an offensive was “low, but possible.”