Members of Kurdish security forces ride in a vehicle at Mount Sinjar, in the town of Sinjar, December 21, 2014.

U.S.-led forces attacked Islamic State of Iraq and Syria (ISIS) targets on Sunday with 13 air strikes in Iraq and three in Syria, using fighters, bombers and other aircraft, the U.S. military said.

Four of the Iraq strikes were near Sinjar in the north of the country, which destroyed ISIS buildings, tactical units and vehicles, while other Iraqi cities targeted included Tal Afar, Ramadi, Mosul and Baiji, according to the Combined Joint Task Force quoted by Reuters.

Earlier, Iraqi Kurdish leader Masoud Barzani hailed victories over ISIS during a visit to Mount Sinjar, which had been besieged by the militants for months.

Thousands of the autonomous Kurdish region’s peshmerga fighters launched a major operation on Wednesday backed by U.S.-led air strikes which broke the second IS siege of Mount Sinjar this year.

The operation threatens the links between the city of Mosul, the main ISIS stronghold in Iraq, and territory the militant group controls in neighbouring Syria.

“During the past 48 hours, the peshmerga opened two main routes to Mount Sinjar,” Barzani said, adding that “we did not expect to achieve all these victories.”

In addition to breaking through to the mountain, “a large part of the center of the town of Sinjar was also liberated,” he said, referring to an area to the mountain’s south.

The Kurdish regional president also said the peshmerga might participate in an operation to retake Mosul itself.

“We will take part if the Iraqi government asks us, and of course we will have our conditions,” he said, without specifying what they would be.

ISIS spearheaded a sweeping militant offensive that has overrun much of Iraq’s Sunni Arab heartland since June, presenting both an opportunity for territorial expansion and an existential threat to the country’s Kurdish region.

Multiple Iraqi divisions collapsed in the early days of the offensive, clearing the way for the Kurds to take control of a swathe of disputed northern territory that they have long wanted to incorporate into their region over Baghdad’s objections.

But after driving south towards Baghdad, ISIS then turned its attention to the Kurds, pushing them back toward their regional capital Arbil in a move that helped spark U.S. air strikes against the jihadists.

Backed by the strikes, which are now being carried out by a coalition of countries, Kurdish forces have clawed back significant ground from ISIS.

The conflict seems set to redraw the internal boundaries of Iraq in favor of broader Kurdish control in the north.

In his remarks on Mount Sinjar, Barzani said: “We will not leave an inch of the land of Kurdistan for (ISIS), and we will strike (ISIS) in any place it is located.”

Tens of thousands of members of the Yazidi religious minority were trapped by ISIS on the mountain for days in the searing August heat in a first siege that sparked fears of genocide.

That siege was broken and many of the civilians evacuated, but others stayed behind and were again besieged by the jihadist group in October.

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