Russia's government has resigned, hours after President Vladimir Putin proposed sweeping constitutional changes that could prolong his stay in power.
PM Dmitry Medvedev said the president's proposals would significantly change Russia's balance of power.
Mr Putin asked Mr Medvedev to become deputy head of the National Security Council, which is chaired by Mr Putin.
The president later nominated tax service chief Mikhail Mishustin to replace Mr Medvedev as prime minister.
The unexpected announcement comes four years before Mr Putin's fourth term of office is due to end.
Under the existing constitution, he would not be entitled to another term.
The Russian leader said during a speech to both chambers of parliament that there would be a nationwide vote on changes that would shift power from the presidency to parliament.
Russian government sources told the BBC that ministers did not know about the government's resignation ahead of the announcement.
"It was a complete surprise," one source said.
Mr Medvedev has been prime minister for several years. He previously served as president from 2008-2012, switching roles with Mr Putin – a close ally – after the latter served his first two terms as president.
Russia's constitution only allows presidents to serve two consecutive terms.
Even when he was prime minister, Mr Putin was widely seen as the power behind then President Medvedev.
"These changes, when they are adopted… will introduce substantial changes not only to an entire range of articles of the constitution, but also to the entire balance of power, the power of the executive, the power of the legislature, the power of judiciary," Mr Medvedev said of Mr Putin's proposals.
"In this context… the government in its current form has resigned."
What is Mr Putin proposing?
At the end of his speech, Mr Putin put forward several constitutional reforms.
They included giving the lower house of parliament, the State Duma, "greater responsibility" for the appointment of the prime minister and the cabinet.
Currently, the president appoints the prime minister and government ministers, and the Duma approves the decision.
Mr Putin also suggested an increased role for an advisory body called the State Council. The council, which is currently chaired by Mr Putin, comprises the heads of Russia's federal regions. Mr Putin said it had proved to be "highly effective".
Other measures include:
- Limiting the supremacy of international law
- Amending the rules that limit presidents to two consecutive terms
- Strengthening laws that prohibit presidential candidates who have held foreign citizenship or foreign residency permits
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Mr Medvedev made his announcement on state television with President Putin sitting next to him. Mr Putin thanked Mr Medvedev for his work but said "not everything" had been accomplished.
BBC Moscow correspondent Sarah Rainsford said the reason why Mr Putin had removed Mr Medvedev was unclear.
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Crazy day in Moscow politics. Basically, Putin has removed Medvedev as PM & will taRead More – Source
