Australia, New Zealand and Japan called for an immediate halt to testing and handed formal protests to French diplomats in their capitals.
South Korea voiced "deep disappointment" while tiny island states near France's nuclear test site bitterly accused it of arrogance.
"France is its own worst enemy," said New Zealand Prime Minister Jim Bolger.
"Its reputation in the Pacific is at an all-time low. When the tests are over France will have to rebuild its credentials in the region," he said.
The blast Wednesday, beneath the remote Mururoa coral atoll about 1,200 kilometers southeast of Tahiti, was weaker than previous blasts, scientists said.
French officials said the tests are needed to develop simulation technology to make future test blasts unnecessary. France had planned eight tests but has reduced the number to six, to be completed by February.
"We are now close to the end of this final campaign," Foreign Ministry spokesman Yves Doutriaux told a daily news briefing Thursday in Paris. "We have been and continue to be part of negotiations to bring about a treaty for a complete ban on nuclear tests."
Doutriaux also said that after testing is completed, a panel from the International Atomic Energy Agency would be able to check the atolls for any radiation contamination.
The United States "continues to urge all nuclear powers, including France, to refrain from further nuclear tests and to join in a global moratorium as we work to complete and sign a comprehensive test ban treaty in 1996," State Department spokesman Glyn Davies said.
Australia's acting prime minister, Kim Beazley, accused France of displaying "arrogant disregard" for a recent United Nations resolution calling for an immediate end to nuclear testing.
Japanese Prime Minister Tomiichi Murayama described France's test program as "fruitless."
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