HELSINKI (Reuters) - Finnish President Sauli Niinisto said on Monday both sides in the war in Ukraine were using heavier weapons, including in Russia's case thermobaric bombs.

       "We are supporting Ukraine with increasingly heavy weaponry. And on the other hand Russia has also begun to use very powerful weapons, thermobaric bombs that are in fact weapons of mass destruction," Niinisto said during security policy talks at his summer residence in Naantali, Finland.

       Ukraine and NATO countries have also accused Russia of using thermobaric bombs, which are also known as vacuum bombs and are much more devastating than conventional explosives.

       Finland and neighbouring Sweden have applied to join NATO following Russia's invasion of Ukraine on Feb. 24.

       (Reporting by Anne Kauranen; Editing by Gareth Jones)