Gilles Jacquier was on a government-authorized trip to the city, the France 2 channel said.
Syrian TV said Gilles Jacquier was among eight killed. A colleague said that minutes earlier they had interviewed some people at a pro-government gathering.
Opposition groups say 15 people died around the country on Wednesday, including three in Homs.
“We vigorously condemn this odious act,” Alain Juppe said in a statement.
The Syrian authorities have severely restricted access to foreign journalists since the unrest began last March.
More than 5,000 people have been killed, the UN says. The government says 2,000 security personnel have died combating “armed gangs and terrorists”.
Observers arrived in Syria in December to monitor an Arab League peace plan, but the killing has continued.
Arab League said on Wednesday it was delaying sending more monitors after an attack on an observer team earlier in the week, Reuters news agency reported.
Eleven observers were slightly injured in the attack, in the port city of Latakia.
Gilles Jacquier, 43, was part of a group of 15 foreign journalists being shown around a part of Homs and speaking to locals.
One of his colleagues said they were escorted by soldiers and police, and were in a part of the flashpoint city where street life was relatively normal with some shops open.
A grenade fell close to them minutes after they had spoken to some young people and they fled into a nearby building. More grenades hit the building causing casualties.
“There was smoke everywhere, people started screaming and yelling. There was complete chaos,” he said.
Gilles Jacquier was behind him when he went into the building, but he saw him lying dead a few minutes later, he added.
At least one other European journalist was wounded, reports say. Dutch officials and media said a Dutch journalist was hurt.
The area of the attack is inhabited by members of the Alawite sect and therefore considered to be mainly pro-government. No opposition supporters have given an account of the incident.
His mission in Syria was to make a documentary film on the protests.
The incident came as Arab League observers continued their mission aimed at monitoring a peace plan proposed by the league.
Earlier on Wednesday, a former member of the mission called it a “farce” and described the situation there as a humanitarian disaster.
Anwar Malek told al-Jazeera TV that he had resigned because of what he had witnessed in Syria, including war crimes committed by security forces.
He said the government had “fabricated” most of what the monitors had seen to stop the Arab League taking action.
The UN Security Council has been told that an estimated 400 people had been killed in Syria since the mission arrived in late December – an average of almost 40 deaths a day.
The US permanent representative to the UN, Susan Rice, said the figure showed Syria’s government had accelerated its killing of demonstrators, rather than using the opportunity to end the violence.
Meanwhile, President Bashar al-Assad made a surprise appearance at an open air rally by thousands of his supporters in Damascus.
Bashar al-Assad said he wanted to show his love for the Syrian people.
His wife, Asmaa, and his children were also briefly shown in the live broadcast. There had been speculation that they might have left Syria.
The US House Ethics Committee has voted to release its report on former Republican Representative…
ABC News has agreed to pay $15 million to President-elect Donald Trump to settle a…
South Korea’s parliament has voted to impeach President Yoon Suk Yeol over his failed attempt…
Israeli war planes have carried out more than 100 air strikes in Syria on December…
President-elect Donald Trump has threatened to impose 100% tariffs on the BRICS countries if they…
Syrian troops have withdrawn from the city of Aleppo following an offensive by rebels opposed…