UK Prime Minister Tony Blair has paid tribute to Boris Yeltsin following the Russian president's surprise resignation.

Mr Blair said Mr Yeltsin had played a crucial role in the development of Russia as a modern, democratic state.

The prime minister said in a statement: "Boris Yeltsin has played a crucial role in the history of Russia.

"He has steered his country through a most difficult and painful transition from communism to democracy.

"At every critical moment, his decisions have reinforced the process of reform and made Russia a closer partner of the west, both politically and economically."

The statement continued: "I have greatly valued working with him as a partner in the G8 and on the many international issues which we have discussed.

"The world is more stable and secure as a result of Boris Yeltsin's leadership.

"We now look forward to the presidential elections when the Russian people will decide on Boris Yeltsin's successor and take a further step towards embedding the democratic process.

"In the meantime, I look forward to continuing to work closely with Prime Minister Putin."

'Historic time'

Later, Foreign Secretary Robin Cook praised Mr Yeltsin's "historic achievements".

He said: "President Yeltsin occupied the presidency of Russia at an historic time for that country.

"He will be remembered for two historic achievements. First, the time when he stood and faced down those who attempted a coup and a return to the old authoritarian ways.

"More than anybody else President Yeltsin recognised Russia had to turn its back on the past and embrace a multi-party democracy."

President Yeltsin would also be remembered for acting as a partner with the west to end the cold war, said Mr Cook.

The foreign secretary said: "We have had our differences but it was always clear that Russia did not seek conflict around the globe."

Mr Cook added it was a final tribute to Mr Yeltsin that one democratically elected president of Russia would now be succeeded by another.

Shadow foreign secretary John Maples said he hoped the UK would maintain good working relations with Russia under Mr Putin.

He said: "President Yeltsin has succeeded in preserving and enhancing Russia's fragile democracy and has built a practical working relationship with the west.

"He has not been so successful with Russia's economic reforms which have been crippled by corruption.

"We must hope acting President Putin can preserve democracy while building economic success.

"The little we know of Mr Putin is from the ruthless prosecution of the war in Chechnya, which we all hope will soon come to an end and that humanitarian disaster will be avoided."