A suspected rebel mortar attack struck a Syrian Red Crescent distribution centre in the government-held city of Aleppo, killing a volunteer and two civilians who had come to seek assistance, the organisation has said.

The attack in the Hamadaniya neighbourhood, which occurred on Wednesday, also wounded seven other volunteers, according to the Syrian Arab Red Crescent and the Red Cross.

The Britain-based Syrian Observatory for Human Rights confirmed the attack, saying that there were other mortar rounds that hit security checkpoints in the area on Wednesday.

Syria's state news agency said mortar shells also hit other buildings in the neighbourhood.

After years of heavy fighting, Syrian government forces drove the rebels out of eastern Aleppo in December, but the opposition still holds some areas on the city's outskirts.

Fighting has continued around Aleppo and in other parts of Syria despite a Russia and Turkey-sponsored ceasefire.

The ceasefire, in place since December 30, has excluded areas where militant factions, Islamic State and Syria's al Qaida affiliate operate or hold ground.

Syrian government troops and allied militias, as well Turkish troops, the US-led international coalition and Russia have been going after IS in different parts of the country.

The push has lately focused on the IS-held town of al-Bab, north east of Aleppo.

Syrian government forces and their allies have been pushing from the south, aided by Russian air strikes.

On Thursday, government troops seized a village south of al-Bab, bringing them less than three kilometres (1.5 miles) from the town, according to opposition monitors.

Meanwhile, Turkish troops, backing Syrian opposition fighters, have pushed their way from the western part of the town, entering the outskirts of al-Bab.

The two advances have effectively encircled the militant group, which had set up strong fortifications around al-Bab, one of IS's last remaining strongholds in northern Syria.

Another fight against IS is raging in east and north east Syria, where Kurdish troops, backed by the United States, are advancing against IS in the militants' de facto capital of Raqqa.

Meanwhile, government forces are battling an IS offensive in Deir al-Zour and another one in the central Homs province, around the ancient town of Palmyra.

Violence has also beset rebel and opposition-held areas, including in Homs, where at least nine civilians were killed in suspected Russian or government air strikes on Wednesday.

AP