MOSCOW - Saudi Arabia’s foreign minister on Tuesday poured cold water on Russian calls to join forces with the Syrian authorities against Islamic State militants, insisting it was impossible to work with President Bashar al-Assad.

Moscow - one of Assad’s few remaining allies - has called for coordination between the Syrian government and members of an international coalition fighting the extremist group, which controls swathes of territory in Syria and Iraq. But Saudi Foreign Minister Adel al-Jubeir insisted there would be no cooperation with the Syrian regime after meeting Russian counterpart Sergei Lavrov in Moscow.

“As for a coalition in which Saudi Arabia would participate with the government of Syria, then we need to exclude that. It is not part of our plans,” Jubeir said in comments translated into Russian. “Our position has not changed... there is no place for Assad in the future of Syria,” Jubeir said. “We think that Bashar al-Assad is part of the problem, not part of the solution.”

Saudi Arabia is already part of a US-led coalition that began an air campaign against IS in Syria last September. Russia supports Assad while Saudi Arabia insists he must quit to help end a four-year conflict that has cost over 240,000 lives.

The two ministers last met in Qatar on August 3 when Lavrov, Jubeir and US Secretary of State John Kerry held a three-way meeting, with Syria topping the agenda. Lavrov said Moscow was not looking to establish a formal alliance against the radical group but warned a failure to cooperate could open the door to the extremists.

He admitted that there remained “persistent differences” between Riyadh and Moscow over how to tackle the Syrian conflict. “The exit of President Assad is part of these differences,” Lavrov said.

At least 25 Syrian rebels were killed overnight in an attack by Islamic State group fighters on an insurgent stronghold in Aleppo province, a monitor said on Tuesday. Fighting lasted until dawn on Tuesday in Marea, one of the most significant rebel bastions in the divided province. The town sits on a road linking eastern Aleppo city and the border with Turkey. At least eight IS fighters died, according to the Syrian Observatory for Human Rights, “including four suicide bombers who blew themselves up with explosive belts”.

Mamun al-Khatib, director of Shahba, an Aleppo-based activist news network, said in a Facebook post that “an IS cell infiltrated the town of Marea and its fighters bombed and fired upon civilians”.

Rebel fighters surrounded the militants, prompting them to blow themselves up, Khatib added. IS militants on Sunday seized full control of Umm Housh, one of four villages in the northern province of Aleppo that lie along a rebel supply line from Turkey, which is a major backer of Syria’s opposition.

At least 37 rebel fighters and 10 IS militants died in the battle for the town, the Observatory said. More than 240,000 people have been killed in Syria since the conflict began with anti-government demonstrations in March 2011.

Meanwhile, , the Turkish coastguard on Tuesday rescued 330 Syrians adrift in the Aegean Sea after failing to reach Greece, as the number of migrants attempting the treacherous passage to Europe surges.

Members of the group said they had been travelling on eight small boats. They included dozens of children, at least five of them newborn, and women, some of whom were visibly pregnant.

“We are told Europe will welcome us, but the door is closed in our face,” said Abdul, 23, from Damascus. “We will try again every day to reach Greece.”

Several of the refugees said their boat had been stopped by armed Greek coastguard officers who ordered them to dump fuel, stranding them at sea.

A spokesman for the Greek coastguard, Nikolaos Lagadianos, said it “categorically denied” the allegations, saying an incident had taken place off the Turkish town of Bodrum, further south, but that the Greek authorities had not been involved.

Crisis-hit Greece has seen a dramatic rise in the number of people seeking refuge. The United Nations refugee agency said 124,000 had arrived this year by sea.

Most are travelling to Greek islands in the Aegean from the nearby Turkish mainland. Turkey is home to more than 1.8 million Syrian refugees escaping the four-year-old civil war.

One Turkish coastguard officer in the seaside resort town of Cesme said his crew had rescued 700 people in the past week, which he said was a record. “There has been a calamitous increase, and we do not have the resources to meet their needs,” the officer said, declining to be named because he is not authorised to speak to the media.

Most are refugees from war-torn Syria, but others fleeing hardship and violence in Afghanistan, Iraq and Iran are also filling up the inflatable boats run by Turkish smugglers.