It is an "absolute necessity for Syria and Russia to stop their military operations against civilian populations, and in particular that the ordeal facing Madaya and all of the besieged Syrian villages come to an end," Fabius told journalists Monday after meeting with Syrian opposition coordinator Riad Hijab.
Hijab, who is a former Syrian prime minister, also held talks with French President Francois Hollande Monday ahead of UN-led talks with the Syrian regime. After the meeting he told French media that there would be no negotiations with the Syrian regime while "foreign forces" were bombing the country.
A statement from Hollande, meanwhile, said that the regime's willingness to negotiate was being judged by "its indiscriminate bombing and its policy of starving whole cities, in flagrant violation of international law".
Both Hollande and Fabius stressed that Syrian President Bashar al-Assad could not remain in power, and Fabius said Paris would consult the UN Security Council to pressure Syria to end indiscriminate attacks.
Dozens of aid trucks headed to Madaya on Monday after an outpouring of international concern and condemnation, as Doctors Without Borders says at least 28 people have died of starvation there since the start of December. Reports have detailed desperate scenes in which residents have been reduced to eating weeds, insects and pets.
Russia began a campaign of air strikes in support of the regime in late September, which it says is targeting the Islamic State armed group and other "terrorists". It has dismissed reports that its raids have killed hundreds of civilians.
Negotiations between Syria's opposition and the regime are set to begin on 25 January in Geneva to seek an end to a conflict that has claimed more than a quarter of a million lives since it began nearly five years ago.
Fabius cited two conditions to negotiations: "the end of air strikes and attacks" and an agenda that is "precise enough and does not leave too much doubt over the key question of who will govern".
France has played an active role in Syria, joining US-led air strikes against the Islamic State group in September and providing logistical support to anti-Assad Syrian rebels it considers moderate, including Kurdish fighters.
Also last year, French authorities launched a criminal investigation into the Assad regime for alleged war crimes including torture and mass killings, based on evidence provided by a former Syrian army photographer.