PARIS -- French bankers and officials scrambled to calm nerves on Thursday after two days of whipsaw trading that saw their banks' market value fall and rise by billions of euros.
By late in the day those efforts appeared to settle markets jittery about the health of French banks and the heavily indebted U.S. and European economies. Economists said the rebound remained very fragile.
The leaders of the eurozone's biggest economies, Germany and France, announced they will meet Tuesday to discuss solutions to Europe's financial difficulties.
French President Nicolas Sarkozy's office said that the two will come up with "joint proposals" on the governance of the eurozone before the end of the summer. Chancellor Angela Merkel's spokesman said the meeting would focus on suggestions for how to improve the zone's economic policy and crisis management.
Bank of France head Christian Noyer blamed "unfounded rumors" for plunges in the shares of top banks, including Societe Generale and BNP Paribas, and said the country's financial institutions were sound. The country's market regulator warned of sanctions against anyone who fuels or profits from rumors that fed the sell-off
Noyer said that French banks' first-half earnings "confirmed their solidity in a difficult economic environment" and that the banks' capital cushions were healthy.
The stocks continued to drop until strong U.S. jobs data helped propell solid gains on Wall Street late in the European trading day. BNP Paribas closed up 0.3 percent and Societe Generale rose 3.7 percent.
The European Union's markets supervisor said regulators were increasing surveillance of financial markets following the days of steep selloffs. Greece on Monday banned short-selling -- profiting from bets on the decline in a share price -- but no other national regulators have followed suit so far. Consob, Italy's stock market watchdog, said it would meet on Friday morning before the markets open to decide whether or not to take measures about short-selling, which has been blamed for contributing to market volatility.
France is taking pains to assure markets that it won't be the next to see its credit rating downgraded.
Sarkozy cut short his holiday Wednesday and ordered his ministers to come up with new budget cuts to ensure that France sticks to deficit-cutting targets.
All three leading credit rating agencies reaffirmed their triple-A assessment of France, and analysts said they could not identify a trigger for the market turmoil.
"There's nothing behind it, it's a market of malintentioned speculators trading on pure rumors," said Marc Touati, an economist at French trading firm Assya Compagnie Financiere.
After Societe Generale, France's second-biggest bank, saw its share price drop nearly 15 percent Wednesday, the bank asked the French market regulator, the AMF, to investigate the rumors that it was on the ropes because of its heavy exposure to debt from troubled eurozone economies.
Societe Generale CEO Frederic Oudea called the rumors "totally unfounded" and "irrational." Speaking on France-Info radio, he urged calm and insisted that the bank's fundamentals are sound.
Oudea said Societe Generale had already accounted for its exposure to Greece's debts in its second quarter earnings.
"S&P is not going to downgrade France any time soon. Nor are Moody's or Fitch," Gary Jenkins of Evolution Securities said. "Growth will be the key to the stability of the ratings for France, U.K and the U.S. over the next 12 months."
He said there will be extra attention to France's release of second-quarter GDP figures on Friday, and warned that France could suffer if it has to spend significant new money to bail out more struggling eurozone states.
France's growth prospects are considerably better than those of Italy and Spain's, but its economic expansion is slowing and it's failed for years to reduce a deficit that stood at 7.1 percent last year. No other eurozone economy with a triple-A rating has a higher debt than France's -- around 85 percent of national income.
Adding to market worries, French presidential elections scheduled for the spring of 2012 may make it difficult for the government to implement further austerity measures at a time when the economy is slowing.
Elsewhere in Europe, Greece announced a rise in unemployment after a series of unpopular austerity measures aimed at dragging it out of debt that sparked troubles across the eurozone.
And Italy's finance minister, Giulio Tremonti, told lawmakers Thursday that tough and speedy measures are needed over the next two years to balance the budget in 2013. The market turbulence has seen Italy's borrowing costs in the markets spike up to uncomfortably high levels.
Melissa Eddy in Berlin contributed to this report.