DAMASCUS, Syria (AP) — Three people were killed on Wednesday in renewed shelling by Syrian rebels of government-held areas in the deeply contested northern city of Aleppo, state media and opposition activists said.

The violence in the city — Syria's largest and once its key commercial center — has been going on for the past 13th days despite intense diplomatic efforts to restore a limited cease-fire that began in late February. The U.N. Security Council due to meet later Wednesday to discuss the escalation.

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.

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-Qaida 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. IS 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.

Meanwhile in Berlin, the German and French foreign ministers were meeting with U.N. envoy for Syria Staffan de Mistura and Syrian opposition leader Riad Hijab as part of efforts to get the moribund peace talks back on track. The Arab League was also to convene a special session in Cairo on the Aleppo crisis.

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Associated Press Writer Sarah El Deeb contributed to this report from Beirut.