Turkish war planes bombed PKK and YPG targets in Iraq's Sinjar region and in northeastern Syria respectively on Tuesday. Around 30 PKK terrorists were killed in Syria and 40 in Iraq, according to the Turkish military.
The strikes are part of a widening campaign against groups affiliated with the PKK, designated a terrorist organisation by Turkey, the US and EU.
The air strikes in Syria targeted the YPG - a key component of the Syrian Democratic Forces (SDF), which are backed by the United States and have been closing in on the Daesh bastion of Raqqa.
An earlier statement by the British-based Syrian Observatory for Human Rights monitoring group had said that least 18 YPG fighters and media officials were killed in the raids. There was no immediate casualty report from the YPG.
Targeting "hot beds of terrorism"
Turkey's military said its armed forces had targeted the PKK in northern Iraq and northeastern Syria early on Tuesday.
The office of the Turkish General Staff said in a statement that the counter-terrorism strikes were carried out around 2:00 am local time (2300 GMT) on Tuesday to target PKK sites on the Sinjar Mountain in northern Iraq and on Karacok Mountain in northeastern Syria.
The aim of the strikes was to prevent the PKK from sending weapons and explosives for attacks inside Turkey, the statement said.
The air operation was conducted "within the scope of international law" and "with the aim of destroying the hot beds of terrorism which target the unity, integrity, and safety of our country and nation," the statement read.
The PKK has waged an on and off three-decade insurgency against the Turkish state. More than 40,000 people have been killed in the conflict.
TRT World 's Ediz Tiyansan reports from the southeastern city of Mardin near Turkey's border with Syria.
Peshmerga deaths "accidental"
Six members of peshmerga forces were killed accidentally on Tuesday in a Turkish air strike in northern Iraq, a senior official said.
"Six people were martyred, five from the peshmerga and the sixth from asayish," Lieutenant General Jabbar Yawar, secretary general of the peshmerga ministry in Iraq's autonomous Kurdish government, said.
General Seme Bosali, a senior peshmerga military commander in Sinjar, said it appeared to be a mistake as the peshmerga forces are not hostile to Turkey.
The peshmerga are the Kurdish Regional Government's armed forces and the asayish is its intelligence service.
The Kurdish Regional Government is a major ally of Turkey in the region. On Tuesday, it demanded that the PKK withdraw from the Sinjar region.
US blacklists Syrian chemists
Tuesday's air strikes came a day after the US Department of Treasury sanctioned 271 employees of Syria's Scientific Studies and Research Center (SSRC) for developing chemical weapons for Syrian regime leader Bashar al Assad.
The move came weeks after a poison gas attack killed scores of people in rebel-held Idlib province in Syria.
"These sweeping sanctions target the scientific support centre for Syrian dictator Bashar al Assad's horrific chemical weapons attack on innocent civilian men, women, and children," US Treasury Secretary Steven Mnuchin said in a statement.
Some of the people blacklisted had worked on Syria's chemical weapons program for more than five years, the treasury said.
The sanction orders US banks to freeze the assets of any employees named, and bans American companies from conducting business with them.
TRT World has more.