Russia and China warned today that the end of the US Federal Reserve's bond-buying programme could have a profound impact on the global economy and urged caution.

The comments were made ahead of the start of the Group of 20 summit in St Petersburg, when economic issues and Syria will top the agenda.

G20 host Russia and China, the world's second largest economy, made clear their concerns about the widely expected 'tapering' of the Fed's multi-billion dollar monetary stimulus policy.

Zhu Guangyao, China's deputy finance minister, urged the US to be "mindful of the spillover effects and work to contribute to the stability of the global financial markets and the steady recovery of the global economy."

But, briefing reporters ahead of a meeting of the BRICS emerging markets caucus during the G20 talks, Zhu played down the possibility of a bailout for any country in financial difficulty.

The country hardest hit, India, has not approached the other BRICS - which include India and South Africa - despite issuing a public appeal last week for joint forex intervention after the rupee tanked, Russia's summit coordinator Ksenia Yudayeva said.

"We didn't agree on specific measures yet," Yudayeva told a separate briefing, adding that the picture would be clearer when G20 finance ministers meet again in October.

"The countries that have faced the biggest recent capital outflows also have quite weak fundamentals," she said, suggesting that both domestic and international factors were at play in the most troubled economies.

Fed chairman Ben Bernanke triggered a selloff in emerging market currencies, stocks and bonds and a flight to the dollar when he in May raised the possibility of winding down the Federal Reserve's $85 billion per month bond-buying programme.

The Fed is widely expected this month to take its first steps to reduce the extraordinary monetary stimulus, with potentially huge implications for a global financial system that has come to depend on a cheap and abundant supply of dollars.

India also expressed concern about the end of the monetary stimulus programme. Arvind Mayaram, economic affairs secretary at India's ministry of finance said: "I think there should be a very strong statement on the G20 having a consensus on the concern about the spillover effects.

"I think if a strong statement is made on these two points, it will have a major calming impact on the markets in the emerging economies," he told reporters ahead of the summit.

Today's meeting of G20 nations is officially about global economic matters, and an agreement to fight tax avoidance by multinationals is expected to be signed.

The group of developed and developing economies formally backed plans to tackle international tax avoidance and evasion at its meeting in July.

The Group of 20 industrialised nations accounts for two-thirds of the world's population and 90% of its output.