Russia has given passports to almost 1.5 million people living in the annexed parts of Ukraine's Donetsk, Luhansk, Zaporizhzhia and Kherson regions since last October, Russian Prime Minister Mikhail Mishustin said on Tuesday.

Moscow claimed the four Ukrainian regions as its own last September, seven months after it launched a full-scale invasion of its neighbour. It does not fully control any of the regions, and the annexations are not recognised internationally.

"Since last October, almost 1.5 million people from the new regions have received a Russian passport," Mishustin told a government meeting. Russian officials call the four territories "the new regions".

Mishustin said some 1.6 million people in the regions were receiving pensions and about 1.5 million were receiving social benefits.

"This support must be provided, I repeat, in a timely manner," he said.

The combined prewar population of the four regions was estimated at approximately 8.9 million, but millions of Ukrainians have been displaced by the war, with many fleeing to other parts of the country or abroad. Also, many men aged between 18 and 60 are now serving in the armed forces.

Russian President Vladimir Putin signed a decree last month giving those living in the annexed parts of Ukraine a path to Russian citizenship, but under the law those who decline or who do not legalise their status face deportation.

Mishustin made no mention of Crimea, the Black Sea peninsula that Russia forcibly annexed from Ukraine in 2014.

Kyiv says it will retake all occupied territory, including Crimea, and has accused Moscow of trying to intimidate its citizens into accepting Russian citizenship.

(Reporting by Reuters; Editing by Gareth Jones)