Asian and European stock markets plummeted again on Friday as investors feared the world is headed into another recession.

Finance officials from 20 of the world's emerging and wealthy nations pledged to launch a coordinated effort to bolster the struggling global economy. But that did little to calm the worries of investors who have watched as $3.4 trillion has been erased from their portfolios this week.

The Hong Kong market fell more than one percent, and European exchanges are recording bigger losses in afternoon trading. U.S. stock future indexes point to more losses on Wall Street after Thursday's substantial selloff sent indexes down more than 3 percent.

Analysts say that investors are skeptical that European leaders will be able to figure out how to stem the government debt contagion on the continent, while economic growth remains sluggish and unemployment high in the U.S., the world's largest economy.

Moody's Investors Service heightened the worries Friday, downgrading the credit ratings of eight Greek banks by two notches. Moody's said it expects the banks will incur losses on Greek loans they hold, because the Athens government “faces significant solvency challenges.”

Commodity prices also fell Friday, with oil dipping below $79 a barrel on the New York market. Gold, often viewed as a safe haven investment, plunged below $1,700 an ounce.

The finance ministers and central bankers issued a statement late Thursday in Washington after global stock markets plunged earlier in the day, amid new worries the world economy is teetering towards another recession.

The G20 officials say they will take “all necessary actions” to preserve the stability of banking systems, by ensuring they are “adequately capitalized and have sufficient access to funding.”

Global markets sustained major losses this week after the U.S. central bank, the Federal Reserve, warned late Wednesday that it sees “significant downside risks” to the already struggling U.S. economy, and that a complete recovery is years away.