Syria conflict: Islamic State seizes villages north of Aleppo
Islamic State has seized control of several villages north of Aleppo, Syria, despite Russian and US air strikes said to be targeting the group.
Moscow says its air force has killed 300 militants over the past 24 hours.
But a BBC correspondent in the area says the strikes seem to be mostly hitting rival rebel groups, allowing Islamic State (IS) to push forward.
A commander of Iran's Revolutionary Guards working with the Syrian army fighting IS has also been killed.
Iran blames IS for the killing of Gen Hussein Hamedani on Thursday, but the exact circumstances remain unclear.
Dozens of fighters have been killed on both sides as Islamic State advanced north of Aleppo on Friday, the London-based Syrian Observatory for Human Rights said.
IS has driven out opposition forces from a number of villages, as well as a military base, the observatory's Rami Abdel Rahman told the AFP news agency.
He says the group is now just over six miles (10km) from northern perimeter of the city and two miles (3km) from pro-government forces stationed at an industrial area.
"IS has never been so close to the city of Aleppo, and this is its biggest advance towards" Syria's second city, Mr Rahman said.
The BBC's Jim Muir in Beirut says that Russian air strikes seem to be mostly hitting other Syrian opposition forces which pose more of a threat to the Moscow-backed Syrian government.
The Russian bombing campaign appears to have weakened these groups, and given IS the opportunity to push forward, he adds.
Iran earlier said Gen Hussein Hamedani, a senior Revolutionary Guards commander, was killed during an advisory mission with the Syrian army near Aleppo on Thursday.
In 2009 Gen Hamedani was subject to European Union sanctions for his role in suppressing protests following the disputed Iranian presidential election.
The general is the latest of a number of Iranian commanders to be killed in Syria.
Iran has been providing Syrian President Bashar al-Assad's army with military advice in its fight against rebels since the civil war broke out in 2011.