Three French terror suspects, including two brothers suspected of a bloody attack on the offices of French satirical newspaper Charlie Hebdo, have been killed at two separate hostage standoff locations on Friday, according to the City Hall of Dammartin.

While the hostage held by the two brothers at Dammartin is reportedly alive, four hostages were announced dead at a second siege at a Paris supermarket, Reuters reported.

The dramatic developments came after sustained gunfire and small explosions erupted at both hostage situations in France, two days after a massacre at the Paris offices of the satirical newspaper left 12 people dead.

Cherif Kouachi and his brother Said, both in their 30s, died on Friday afternoon after anti-terrorist forces and police officers moved in on a print shop in the small industrial town of Dammartin-en-Goele, northeast of Paris, where the chief suspects in Wednesday's attack had been holed up with a male employee hostage, an official said.

As the principal suspects emerged from a warehouse where they had been hiding and began firing at the police, they were immediately cut down and killed in return gunfire from a large force of police on the scene, said Audrey Taupenas, a spokeswoman for Dammartin-en-Goele City Hall.

Minutes later police broke the second siege at a Jewish supermarket in eastern Paris, where several hostages were seen fleeing from the market after four explosions followed by a barrage of gunfire rocked the building, the Associated Press reported. Shortly after, ambulances and fire trucks were witnessed rushing to the scene, loading victims and driving away.

Out of five hostages, four had been killed, authorities said. But it remains unclear who killed them and when.

Gunman Amedy Coulibaly, who had stormed into the market hours earlier and held customers and staff hostage, was also confirmed to be among the dead. The 32-year-old, along with Hayet Boumeddiene, was involved in fatally shooting a policewoman south of Paris on Thursday, authorities said, adding that his accomplice might have escaped while other shoppers fled the store.

The two simultaneous hostage-takings in France were linked, with suspected gunmen in each situation connected through an earlier attempt to break a convicted terrorist, Smain Ali Belkacem, out of jail, Paris' public prosecutor told ABC News.

At 3 p.m. local time, Coulibaly reportedly called BFM-TV and confirmed that he had "synchronized" his attack with the Kouachi brothers, according to The Irish Times.

Speaking to reporters on Friday evening, French President Francois Hollande thanked the security personnel who ended the standoffs and neutralized the terrorists.

"France isn't done with the threats it is targeted with," Hollande said during his evening TV statement. "We call on vigilance, unity and mobilization."

"We are a free people that don't give in to any pressure," he added. "We carry an ideal that is larger than us. We will defend it everywhere that peace is threatened."

Meanwhile, U.S. President Barack Obama said his country would stand with France in supporting liberty and subverting extremism, CNN reported.

The spirit of solidarity "will endure forever, long after the scourge of terrorism has vanished from this world," Obama said, speaking from Knoxville, Tenn.