The U.S. and Russia have reached an agreement to extend Syria's fragile cease-fire to the northern city of Aleppo, where violence has escalated in recent days, U.S. officials said Wednesday.

The truce went into effect at 12:01am Damascus time on Wednesday. The agreement follows an earlier deal to reaffirm the truce in the Damascus suburbs and coastal Latakia province.

Despite the cease-fire, three people were killed Wednesday in Aleppo, though officials say overall violence in the deeply contested northern city has decreased since the truce’s inception, state media and opposition activists reported.

Aleppo — Syria's largest city and once its key commercial center — has been engulfed in fighting since the unraveling of a limited cease-fire that began in late February. Nearly 300 people have been killed during this latest spate of violence in Aleppo, which has put the city at the center of the Syrian conflict and shattered the partial cease-fire.

Over the last two weeks, hospitals and civilian areas in the divided city have come under attack from government warplanes, as well as shelling from rebel forces.

Speaking at an emergency U.N. Security Council session, U.S. Ambassador Samantha Power called the hospital attacks "reprehensible." She added, "All of us here must work relentlessly to restore and maintain the respite from violence that Syrians yearn for and deserve."

State TV said government troops repelled an overnight rebel attack on an Aleppo suburb controlled by the government.

Pro-opposition activists confirmed that report, adding that government forces regained control of a former mall that had become a new front line with rebel fighters in the western part of the city.

The head of the Britain-based Syrian Observatory for Human Rights Rami Abdurrahman described those clashes as some of the worst between the government and rebel fighters over the last year in Aleppo.

Areas under the control of the Islamic State group and its main rival, the Syrian Al Qaeda affiliate known as the Nusra Front, have not been included in the cease-fire.

Also Wednesday, the Islamic State group said it has advanced in the strategic Shaer gas fields in the central Homs province, overrunning 13 government checkpoints and capturing a Syrian soldier. ISIS said it was getting close to Shaer gas company headquarters and posted photographs said to be of the captured soldier on social media accounts.

There was no comment from the Syrian government on the reported capture of the soldier.

The Observatory, a monitoring group that relies on a network of activists on the ground in Syria, said the Islamic State group seized control of significant parts of the gas field after three days of clashes with government troops there.

The strategic Shaer gas fields have been coveted by the militant group, which has briefly controlled them in the past two years. The massive fields supply commercial gas to the national grid.

The Associated Press contributed to this report.