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Zana Ahmed, Associated Press
A member of the Kurdish forces stands next to an armored vehicle destroyed by an improvised explosive device placed by Islamic State militants that killed several Peshmerga fighters and injured dozens late Wednesday, when they pushed towards Sinjar Mountain, as they inspect the aftermath of the site in Kasr Reej, Iraq, Thursday, Dec. 18, 2014. Iraqi Kurdish forces battling Islamic State militants managed on Thursday to open up a corridor to the mountain so that thousands of people from the country's Yazidi minority who have been trapped there can flee, said a senior Kurdish official.

KOBAN, Iraq — Iraqi Kurdish forces battling Islamic State militants managed on Thursday to open up a key corridor so that thousands of people from the country's Yazidi minority who have been trapped on a mountain can flee, said a senior Kurdish official.

The development was an incremental step in the battle to retake the town of Sinjar, at the foothills of the mountain by the same name, which fell to the Islamic State group in early August.

The Kurdish peshmerga troops, backed by U.S.-led coalition airstrikes, launched the operation to retake Sinjar on Wednesday.

Masrur Barzani, chancellor of Kurdistan Region Security Council, said the Kurdish forces advanced in battle, establishing the passageway to the mountain on Thursday. He emphasized that Iraqi forces were in no way part of the operation.

"We asked the Iraqi government to provide the ammunition needed for this operation. Unfortunately they did not send the ammunition and their contribution was nothing, to be quite frank with you, especially for this operation," Barzani told The Associated Press in Dohuk, in Iraq's Kurdish region.

Tens of thousands of Yazidis became trapped on the mountain in early August, when the IS extremists captured the towns of Sinjar and Zumar, prompting the exodus.

Many were eventually airlifted off the mountain or escorted by a passageway through Syria back into Iraq, where they found refuge in the Iraqi Kurdish semi-autonomous region. But thousands remained stuck on the mountain.

"A corridor has been opened to evacuate those people," Barzani said.

Yazidis follow an ancient religion with ties to Zoroastrianism.

Associated Press writer Sameer N. Yacoub contributed to this report from Baghdad.