The motive for the attacks, which prompted heightened security at media offices and the busy Champs-Elysées shopping avenue, is unclear.
Paris prosecutor François Molins said authorities believe a lone gunman was involved in the shooting at the prominent daily newspaper Libération, a similar incident at news network BFM-TV, a shooting at French bank Société Générale and a brief hostage-taking.
Authorities released video footage of the suspect. Molins said he was wielding a pump-action rifle and wearing a black vest, green shoes with white soles, and a cap. Molins said the suspect's image will be distributed publicly to help with the manhunt.
Monday began with a gunman entering the lobby of Libération around 10am and opening fire. A 27-year-old photographer's assistant was in intensive care after being shot near the heart and in the arm, Molins told a news conference.
The shooting prompted cries of concern about attacks on the media. The culture minister called Libération – an outspoken left-leaning paper founded by Jean-Paul Sartre – a "pillar of our democracy".
Less than two hours after the shooting at Libération, three shots were fired in front of the headquarters of the bank Société Générale in the Paris suburb of La Défense, according to Paris police. Société Générale, based about 10 kilometers northwest of the Libération offices, said in a statement that a lone gunman opened fire in front of the building and that no one was hurt.
Less than an hour later a man called police to say he had been taken hostage by a gunman in the town of Puteaux, close to La Défense. Police said the gunman forced his hostage to drive six kilometres back toward central Paris, then let him go on the Champs-Elysées, a chic and busy shopping thoroughfare.
Police were searching the neighbourhood and other sites around the French capital.
All this came three days after an incident at BFM-TV, in which an armed man threatened journalists with a rifle in the news network's lobby before fleeing. He left behind unused cartridges, and told witnesses, "Next time, I won't miss", Molins said. It was unclear whether the gunman's rifle malfunctioned or whether he chose not to shoot.
"Taking into account the similarities of these four affairs, in the modus operandi, the clothing of the perpetrator and in the munitions that were recovered, we believe a single gunman is the most likely possibility," Molins said.
The government positioned police at all major media organisations in Paris, according to Interior Minister Manuel Valls. A helicopter flew over the neighbourhood that includes the French president's office and the Champs-Elysées avenue.
French President François Hollande said he ordered authorities to "mobilise all means to clarify the circumstances of these acts and arrest the perpetrator or perpetrators".
Media watchdog Reporters Without Borders denounced the attacks on the journalism facilities. – Sapa-AP