A day after the Federal Reserve announced another measure to bolster the economy, world financial markets tumbled Thursday on fears that governments around the globe collectively still were not doing enough to stimulate growth.

Several factors contributed to the heightened gloom, including new signs of political paralysis in Washington, Europe’s continued failure to resolve its debt crisis and indications of economic stress in developing countries that had been strong.

While the Fed’s measures to lower interest rates could increase growth a bit, some economists worry that the scale of the problems call for more stimulus efforts globally, but other countries are not cooperating.

With investors so nervous, the markets may rebound over the next few days, as volatility and big swings of 3 and 4 percent have become more common. On Thursday a downcast mood appeared across the board. Stocks plunged about 5 percent across Europe and in Hong Kong, and more than 3 percent in the United States.