Members of a massive Dutch motorcycle gang, armed with Kalashnikov rifles, recently joined Kurdish forces battling the Islamic State in Iraq, vowing to “exterminate the rodents.”

The leader of No Surrender -- which has dozens of chapters in the Netherlands and across Europe -- told state broadcaster NOS on Friday that three of its members have traveled to Mosul in Northern Iraq to take up the fight against ISIS, AFP reports.

A photo posted on a Dutch-Kurdish Twitter account last week shows a heavily-tattooed man in military garb flashing the “victory” sign alongside a Kurdish fighter inside a bunker.

“Ron from The Netherlands has joined the Kurds to exterminate the rodents of [ISIS],” a caption with the photo reads, according to the New York Post.

Countries around the world have been trying to stop people from joining the jihadists in the Islamic State, but a Dutch public prosecutor says it’s OK for its citizens to fight against them.

"Joining a foreign armed force was previously punishable, now it's no longer forbidden," Wim de Bruin told AFP on Tuesday. "You just can't join a fight against the Netherlands."

Dutch citizens are also not allowed to join the Kurdistan Workers' Party because it is blacklisted as a terrorist organization, De Bruin added.

Meanwhile, Kurdish militiamen fought pitched street battles Wednesday with the extremists in a Syrian Kurdish border town near Turkey, making small advances, activists and officials told The Associated Press.

In the border town of Kobani, members of the Kurdish People's Protection Units, or YPG, were advancing hours after the U.S.-led coalition stepped up airstrikes against ISIS in and around the town, said Asya Abdullah, a Syrian Kurdish leader.

Abdullah, the co-president of Syria's powerful Kurdish Democratic Union Party, or PYD, told The Associated Press that Kurdish fighters have advanced near the hill of Tel Shair that overlooks part of the town, taking advantage of the air raids that slowed the push by the militants. Abdullah spoke by phone from Kobani.

U.S. Central Command said Wednesday that 18 airstrikes near Kobani destroyed 16 ISIS-occupied buildings. One airstrike near the Haditha Dam in western Iraq destroyed an ISIS armed vehicle and guard shack, while four airstrikes in Baiji destroyed an ISIS building, a Humvee and artillery.

In mid-September, the Islamic State group launched its offensive on Kobani -- also known under its Arabic name of Ayn Arab -- and captured dozens of nearby Kurdish villages, as well as about a third of the town. The fighting in and around Kobani has killed more than 500 people and forced more than 200,000 people to flee across the border into Turkey.

The Britain-based Syrian Observatory for Human Rights, which has a network of activists around the country, said Wednesday's clashes were taking place in the eastern neighborhoods of Kobani as well as the southern edge of the town.

The Observatory also reported several airstrikes by the U.S.-led coalition in the town Wednesday and plumes of smoke rising from the strikes were visible across the border in Turkey.

Also Wednesday, Syria's Foreign Ministry dismissed Turkey's calls for a no-fly zone on the Syrian territories as a "flagrant violation" of the U.N. charter and international law.

"Syria categorically rejects the establishment of no-fly zones on any part of the Syrian territories under any pretext," the ministry said.

Turkey has said it won't join the fight against the Islamic State extremists in Syria unless the U.S.-led coalition also goes after the government of Syrian President Bashar Assad, including establishing a no-fly zone and a buffer zone along the Turkish border.

The Associated Press contributed to this report.