The government of Russian Prime Minister Dmitry Medvedev is to resign, hours after President Vladimir Putin announced plans in parliament to change the constitution.

Mr Putin has asked the PM to move to the post of deputy head of the National Security Council, reports say.

Mr Medvedev said the president's proposals would significantly change Russia's balance of power.

"In this context... the government in its current form has resigned."

The announcement came as a surprise, and in a statement Mr Putin thanked the government for what it had achieved.

President Putin's fourth term in office is due to end in 2024, and under the existing constitution he would not be entitled to another term.

Mr Medvedev told the Tass news agency that the constitutional changes proposed by President Putin would 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".