World leaders have called for unity as global financial markets continue to be gripped by panic.

In the UK, Prime Minister Gordon Brown called for a "global solution" to the meltdown while in Washington, President George W Bush made a public appeal for trust that his country could cut through the "uncertainty and fear" of the crisis.

Mr Bush acknowledged the problem is global and that his forthcoming meeting with G7 finance ministers, including Chancellor Alistair Darling, is vital.

The US leader said: "The world is sending an unmistakable signal: We're in this together and we will come through this together. The US government is acting. We will continue to act to resolve this crisis.

"The Federal Government has a comprehensive strategy. We can solve this crisis and we will."

As markets rollercoastered on Friday, London's FTSE 100 Index closed at 3932, down 382 points. On Wall Street, the Dow Jones Industrial Average plunged almost 700 points at one stage.

The White House later dismissed suggestions that US markets could be suspended so international financial rules are rewritten amid the turmoil that has gripped markets for weeks.

Spokesman Tony Fratto said: "There are absolutely no plans or discussions to interfere with the functioning of markets in the United States."

Henk Potts, director of investment strategy at Barclays Stockbrokers, said: "I think it's very close to panic. We are drowning in a sea of red numbers and fundamentals have gone out the window."

Mr Brown has urged other countries to follow Britain's lead in injecting billions of pounds into their ailing banks and said: "Because this is a global problem, it requires a global solution."

During a visit to Swindon, Mr Brown said the £500 billion rescue package for the British banking system was the "right decision".

He said: "We are trying to get banks to do what they have traditionally done. We are restructuring the banking system and we are doing everything we can. What we need now is for other countries to do similar things."

He reiterated his earlier message, saying: "This is a global problem and I'm trying to get other countries to do what we have done."

The Prime Minister said "it will take a few days" for the measures put in place in Britain to play out in the markets.

He also called for new cross-border rules on transparency and new standards of conduct to end irresponsible risk-taking.