Syrian troops loyal to President Bashar al-Assad and Russian forces on Tuesday halted airstrikes on the city of Aleppo ahead of a planned “humanitarian pause” in fighting on Thursday, Reuters reported. Russian Defence Minister Sergei Shoigu said the move was implemented to allow rebel fighters and civilians to leave the city without being affected by the fighting.

Shoigu further said that the halt in fighting would also guarantee the safety of sick and wounded people who are being evacuated from the city. “We call on the leadership of countries that have influence over armed groups in eastern Aleppo to convince their leaders to stop military action and abandon the city,” the minister said in an apparent reference to the United States, which supports some rebel groups.

However, the groups have rejected the offer and have said that they will not withdraw from the city. “The factions completely reject any exit – this is surrender,” said Zakaria Malahifji, a political officer of the Fastaqim group. A commander of Islamist group Ahrar al-Sham also denied claims that there were extremist militants in the rebel-held portion of the Syrian city, according to The Guardian.

Meanwhile, the United Nations said it needed “assurances from all parties” that the eight-hour-long ceasefire on Thursday would be respected. UN spokesperson Jens Laerke said, “We need everybody to give us those assurances before we do anything meaningful.”

Fighting between forces loyal to Assad and rebel groups intensified after a ceasefire deal broke down in September when an aid convoy was bombed in Aleppo. More than 3,00,000 people have died in the six-year-long civil war and nearly half the country’s population has been forced to flee since it began.