Tens of thousands of Syrian Kurds have fled across the border into Turkey in the last 24 hours to escape Islamic State (Isis) fighters, the Turkish government has said.

The country opened eight crossing points along a 20-mile (32km) stretch from Akcakale to Mursitpinar, allowing about 45,000 Kurds to escape from the Islamist extremists, the deputy prime minister, Numan Kurtulmus, said on Saturday.

The exodus began as Isis fighters seized control of 60 Kurdish villages near the border in a two-day campaign as they approach the town of Kobane, also known as Ain al-Arab.

At least 18 militants from Isis, which is also known as Isil, were killed in heavy clashes with Kurdish fighters in the area overnight, according to the British-based Syrian Observatory for Human Rights.

The news of the exodus came as Turkey announced that Isis had released 49 Turkish hostages, including diplomatic staff, who were seized in Mosul, Iraq, on 11 June when militants stormed the Turkish consulate.

Kobane, in Aleppo province, is Syria's third-largest Kurdish town and would give Isis control of a long stretch of the country's northern border with Turkey, which fears that a further 100,000 Kurds could seek refuge as they flee possible reprisal attacks by the jihadists.

Syria's exiled opposition National Coalition has warned of "the danger of a massacre" in the area, where Kurdish fighters, who have resisted Isis for months, have been forced to retreat in recent days.

A spokesperson for the People's Protection Units, one of the Kurdish groups battling Isis, said his fighters' weapons were no match for the looted US arms the militants took from fleeing Iraqi soldiers in June.

"Isis has highly advanced and sophisticated American weapons. We need weapons too," said Redur Xelil. "Isis is now aiming to take over Kobane, as they aimed to take over Erbil."

Masoud Barzani, the Iraqi Kurdish leader, has called for international action to protect the Kobane region, saying the insurgents must be "hit and destroyed wherever they are".

France mounted its first air strikes against the militants in Iraq on Friday, destroying ammunition stores, vehicles and fuel reserves in the Mosul area, while the US is drawing up plans for military action against Isis in Syria.

The US secretary of state, John Kerry, met representatives of 35 countries, including Iran, on Friday to bolster support for the campaign against the jihadists.

He said after the meeting at the UN security council in New York that the grouping, which includes Britain, Turkey, Saudi Arabia and Qatar, showed "the clear need for all of us to come together, to welcome and to support the new inclusive government in Iraq and of course to put an end to Isil's unfettered barbarity".

Tehran is backing both Iraq and Syria in their battle against the Islamic State group, and Kerry said there was "a role for nearly every country to play, including Iran" in combating the jihadist threat.