Four people were stabbed on Friday near the old offices of the Charlie Hebdo satirical magazine in Paris, Prime Minister Jean Castex said.
A police source had earlier told Reuters that two of the four wounded had life-threatening injuries.
A source said two suspects were on the run and that a security cordon had been set up because of a suspect package.
A blade was found at the scene, two police sources said. One described it as a machete, the other called it a meat cleaver.
Local authorities asked people to avoid the area and said a police operation was ongoing in a northeastern district of the capital. Deputy mayor Emmanuel Gregoire tweeted that police were hunting a "potentially dangerous" individual.
The attack comes three weeks after 14 people with suspected links to homegrown Islamist militants who attacked the Charlie Hebdo offices in January 2015, killing 12 people, went on trial in Paris.
The court heard that they had sought to avenge the Prophet Mohammad, nearly a decade after the weekly published cartoons mocking him.
