Legislators in Russia's lower house State Duma on Thursday unanimously approved a bill to amend the constitution submitted by President Vladimir Putin - the first of three readings.

All 432 legislators present voted in favour of the bill, part of Putin's major reform plan unveiled last week, after debating the proposed amendments for less than two hours.

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"This was a powerful show of unity," speaker Vyacheslav Volodin said after the vote by the pro-Putin chamber.

The Communist faction in parliament, despite voting for the bill, will prepare suggestions for the second reading, said party leader Gennady Zyuganov.

The second reading, usually considered key for Russian bills, is expected on February 11, Volodin said.

The current Russian constitution, in effect since 1993, was written under then-President Boris Yeltsin following a constitutional crisis sparked by his conflict with lawmakers who opposed increasing presidential powers.

Putin's proposed shake-up of Russia's power structures has sparked speculation over his intentions after his current term as president expires in 2024, with analysts suggesting the 67-year-old may be carving out a "father-of-the-nation" role for himself.

The reforms shift some of the country's major powers away from the presidency towards the parliament and the influential State Council.

Hours after Putin proposed the constitutional changes at his annual address to legislators last week, Prime Minister Dmitry Medvedev and his entire government resigned to make way for a cabinet hand-picked by the president.

Medvedev, a longtime Putin ally, was rewarded with a position as the deputy chief of the State Council, overseeing the nation's defence and security portfolios.

Wield power

Putin's pick for his replacement as prime minister, a former tax official named Mikhail Mishustin, was approved by the Duma last week. Analysts say he is unlikely to challenge Putin over any of the proposed reforms.

Critics have long said Putin, a former KGB officer, wants to stay on in some capacity after his term ends so he can wield power over the world's geographically largest nation and one of its two biggest nuclear powers. He has been in power in Russia, either as president or prime minister, since 1999.

Putin's new government features several familiar faces - the finance, foreign, defence, energy and agriculture ministers all kept their jobs - though the economy minister and first deputy prime minister were both replaced, along with the prime minister.

"The most important task is to increase the welfare of our citizens and strengthen our statehood and the position of our country in the world. All these are absolutely attainable goals," Putin told his new government on Tuesday.

"We have achieved a very balanced government. We have enough people who worked in the previous government, as well as a major renewal."