Fighters from the Kurdish People's Protection Units (YPG) inspect the damage at their headquarters after it was hit by Turkish airstrikes in Mount Karachok near Malikiya, Syria April 25, 2017. REUTERS/ Rodi Said

WASHINGTON (Reuters) - The United States on Tuesday expressed “deep concern” over Turkish air strikes against Kurdish fighters in Syria and Iraq and said they were not authorized by the U.S.-led coalition fighting Islamic State.

The raids in Iraq’s Sinjar region and northeast Syria killed at least 20 in a campaign against groups linked to the outlawed Kurdistan Workers Party (PKK), which has waged a three-decade insurgency against Turkey for Kurdish autonomy.

Turkey is part of the U.S.-led military coalition fighting militants in Syria.

Ankara has strongly opposed Washington’s support for Syrian Kurdish YPG fighters who are part of the Syrian Democratic Forces (SDF), which have been closing in on the Islamic State bastion of Raqqa.

“We have expressed those concerns with the government of Turkey directly,” State Department spokesman Mark Toner told reporters on a conference call.

“These air strikes were not approved by the coalition and led to the unfortunate loss of life of our partner forces in the fight against” Islamic State, he said.

Toner said while the United States recognized Turkey’s concerns with the PKK, the cross-border raids harmed the coalition’s efforts to fight Islamic State.

“We recognize their concerns about the PKK but these kinds of actions frankly harm the coalition’s efforts to go after ISIS and frankly harm our partners on the ground who are conducting that fight,” he added.