President Vladimir Putin vowed on Thursday to fight on in Ukraine until Moscow secures the country's "demilitarisation", "denazification" and neutrality unless Kyiv accepts a deal that achieves those goals.

Fielding questions from the public, media, and at one point frontline soldiers, Putin took an uncompromising stance on Ukraine at a four-hour press conference held as he seeks another six-year presidential term in March.

Putin, now 71, told Russians his initial goals in Ukraine had not changed and that Russian forces had taken the initiative on the battlefield in the "special military operation" he launched on February 24, 2022.

"Practically along the entire line of contact, our armed forces are, shall we say, modestly improving their position. Virtually all are in an active stage of action," Putin said.

Since the start of the war, Kyiv has stepped up its pursuit of Nato and EU membership, steps that it regards as vital for its self-defence and independence from Russia but are opposed by Moscow.

Putin reiterated his view that the Western military alliance's eastward expansion was the main cause of the war - a view dismissed by the West, which sees Putin as the aggressor.

"There will be peace when we achieve our goals...As for demilitarisation, if they (the Ukrainians) don't want to come to an agreement — well, then we are forced to take other measures, including military ones.