TEHRAN - Islamic State group militants have killed a senior commander in Iran's Revolutionary Guards in Syria, the elite branch of the Iranian military said Friday.

General Hossein Hamedani was killed on Thursday by IS "during an advisory mission" in the northern region of Aleppo, a Guards statement said. Hamedani had been playing an "important role... reinforcing the front of Islamic resistance against the terrorists", it added.

Ali Shamkhani, secretary of Iran's Supreme National Security Council, described Hamedani's death as "a huge loss" in the fight against militant groups in Syria. Quoted by the IRNA news agency, he said the loss would be "avenged" and that this would lead to the "complete destruction" of these groups.

Shia-dominated Iran is a staunch ally of President Bashar al-Assad, sending Guards forces and military advisers to aid him against Sunni Muslim rebels seeking his overthrow. Lebanon's Shia militia Hezbollah has done much of the fighting to prop up the Syrian army, though the commander of the Revolutionary Guards' foreign wing, Qassem Soleimani, is said to be heavily involved in guiding military strategy.

Islamic State group fighters advanced Friday to the outskirts of Syria's second city Aleppo, despite 10 days of Russian air strikes that Moscow says are aimed at routing the militants. Moscow announced on Friday that its raids had killed several hundred IS fighters and hit more than 60 "terrorist targets" in Syria over the past 24 hours. Deputy head of the Russian General Staff Lieutenant General Igor Makushev told reporters that "Su-34M and SU-24SM warplanes hit 60 terrorist targets". He said Russia had bombed a command post in IS stronghold Raqa, killing two senior field commanders and some 200 fighters, according to intercepted radio communications.

A Syrian photojournalist working for Turkey's state-run Anatolia news agency in Syria has been killed in a car bomb attack, the media outlet said Friday.

Saleh Mahmoud Laila was killed along with at least 19 others in the attack Thursday on a market in the town of Hraytan in Aleppo province suspected to have been carried out by Islamic State (IS) militants, Anatolia said. It said Laila, 27, had already survived an air strike last July carried out by forces of President Bashar al-Assad that left him with multiple burns and required hospitalisation in Turkey.

President Recep Tayyip Erdogan said in a message that he had learnt of Laila's death "with sadness" and passed his condolences to the photographer's family and the news agency itself.

He said that Laila had worked with "complete understanding and devotion" and his images would be remembered with respect.

The agency paid tribute to Laila's work in "difficult conditions" to show the world what was happening in Syria.

Strikes on Aleppo killed "some 100 militants", and other raids struck command posts and training camps in Latakia, Hama and Idlib. The militants are now just over 10 kilometres (six miles) from the northern edges of Aleppo city and three kilometres (two miles) from pro-regime forces positioned at the Sheikh Najjar industrial zone.

"IS has never been so close to the city of Aleppo, and this is its biggest advance towards" the country's pre-war commercial capital, Abdel Rahman said.

IS has not had a presence in the city, but the militant group on Friday boasted it had "reached the gates of Aleppo".

"IS announced several times that it would launch an offensive on Aleppo without doing it. They were waiting for the right moment and took advance of Russian strikes on other rebels to advance," said jihadism analyst Romain Caillet.

According to the Observatory, 16 IS militants including three child soldiers were killed in the raids which hit "a training camp" on the southern edges of Raqa city.

The Russian air war has provided cover for Assad's ground troops, who have lost swathes of the country to militants and rebel groups since 2011.

The campaign has been critical for the regime's fight in Sahl al-Ghab, a strategic plain in Hama province bordering both the regime's coastal bastion of Latakia and the rebel stronghold of Idlib province.

Syria's army announced a "vast offensive" on Thursday, advancing near Sahl al-Ghab from both the Hama and Latakia fronts with Russian air support. Moscow denied a US claim that four Syria-bound Russian cruise missiles fired from the Caspian Sea had crashed in Iran on Wednesday. "Any professional knows that during these operations we always fix the target before and after impact. All our cruise missiles hit their target," spokesman General Igor Konashenkov said.

Iran declined to confirm the claim by a US official, who did not provide details about where the missiles might have come down or if they caused any damage.

According to the Committee to Protect Journalists (CPJ), Syria is the most dangerous country in the world for journalists. Since the conflict began in 2011, at least 85 journalists have been killed by crossfire, on dangerous assignments, or murdered, it said.