The head of Estonia's military intelligence agency has suggested that Russia still has around four million artillery shells to use in its invasion of Ukraine.

Ants Kiviselg said Russia could continue the war for another year based on the assumption that it uses 10,000 rounds per day, according to a report last Friday from an Estonian media outlet.

Kiviselg said roughly 300,000 shells have been additionally supplied from North Korea, and that this amount may be enough to last about one month. He said the shipments from North Korea indicate that Russia plans to continue its invasion for a long time.

Kiviselg said Russian forces still have significant capabilities and are able to bring in additional contracted and volunteer soldiers to keep the frontlines stable.

Kiviselg said the Russian military's current main objective is to regain its initiative, such as by depriving Ukrainian forces of their offensive potential. He said Russia is ramping up its offensive ahead of the arrival of wet and muddy conditions on the ground, which he said would make the maneuvering of vehicles far more challenging.

Estonia, a NATO member country that borders Russia, has grown wary of the neighboring country since the start of the invasion. It is regularly releasing its analyses of the situation.