Police sources said the suspect attacked a 42-year-old police commander with a knife in front of his home in Magnanville, about 55 kilometers (32 miles) from the French capital, late Monday. The assailant went on to barricade himself inside the house, taking the policeman's wife and son hostage.

Elite police commandos surrounded the property and forced their way inside after attempting for a number of hours to negotiate with the man. The suspect was shot dead during the operation.

Interior Ministry Spokesman Pierre-Henry Brandet told reporters that police had managed to rescue a three-year-old boy from the home, but that the policeman and his partner had been found dead. The slain policeman reportedly worked in nearby Les Mureaux, while his partner was a civil servant with the interior ministry. Their identities have been withheld.

"The investigation is beginning. We have no indication - serious (indication) - on the motivation behind this act," French prosecutor Vincent Lesclous said. Witnesses have, however, told the French AFP news agency that they heard the suspect shout "Allahu Akbar" (God is great) as he killed the police officer.

Various sources have meanwhile identified the assailant as a 25-year-old who had previously been sentenced for "criminal association with the aim of preparing terrorist acts" in 2013, resulting in a three-year prison sentence. He has also been described as having links to Pakistan.

Possible 'IS' link

The Amaq news agency linked to "Islamic State" (IS) cited an unnamed "source" as saying the man was a militant who associated himself with IS. If it is confirmed that IS is directly behind the murders, it would be the first militant strike in France since the government imposed a state of emergency after the November Paris attacks that killed 130 people.

French President Francois Hollande condemned the attack as an "odious act," and said an emergency meeting would be held at his Elysee office on Tuesday.

"Light will be shed on the circumstances of this abominable drama whose investigation, under the authority of justice, will determine the exact nature," Hollande said in a statement.

Hollande added later that the stabbing attack was "incontestably a terrorist act."

nm,ss/bw,kl (AFP, AP)