At least 18 Kurdish YPG fighters and media officials were killed in Turkish air strikes on a headquarters of the militia in northeastern Syria on Tuesday, the British-based Syrian Observatory for Human Rights monitoring group said. Turkey's military bombed the YPG and Kurdish militants in neighboring Iraq early on Tuesday, widening a campaign against groups affiliated with the outlawed Kurdistan Workers Party (PKK). A Syrian Kurdish militia force said the strikes hit a media center, a local radio station, a communication headquarters and some military posts, killing an undetermined number of fighters in Syria's northeastern Hassakeh province. The Britain-based Syrian Observatory for Human Rights, which monitors the Syrian war, also reported the strikes on the media and military targets in Karachok, adding that an airstrike killed three members of the Syrian Kurdish militia known as the People's Protection Units, or YPG. Ankara says members of the outlawed Kurdistan Workers' Party, or PKK, are finding sanctuaries in neighboring Iraq and Syria, among those countries' own Kurdish minorities. A Turkish military statement said the pre-dawn strikes hit targets on the Sinjar Mountain in northern Iraq and also in a mountainous region in Syria. It said the operations were conducted to prevent infiltration of Kurdish rebels, weapons, ammunition and explosives from those areas into Turkey. A Turkish security official, speaking on condition of anonymity in line with Turkish government protocol, said the air strikes are believed to have killed around 200 Kurdish militants, including some senior commanders. The claim could not be independently confirmed. Although Turkey regularly carries out airstrikes against PKK targets in northern Iraq, this was the first time it has struck the Sinjar region. Turkey has long claimed that the area was becoming a hotbed for PKK rebels. Last year, Turkey sent troops into Syria to back Syrian opposition fighters in the battle against the Islamic State group and also to curb what is perceives as the territorial expansion of US-backed Syrian Kurdish forces, which it claims are affiliated with the PKK. The Kurdish group, which has led an insurgency in southeast Turkey since 1984, is considered a terror organization by Turkey and its allies. In its statement, the military vowed to press ahead with operations against the PKK both inside Turkey and across its borders until the "last terrorist is eliminated." The Syrian Kurdish forces denounced Tuesday's strikes on their positions as "treacherous," accusing Turkey of undermining the anti-terrorism fight. Aside from aspirations for autonomy, the Kurdish group in Syria is part of the US-led international coalition against the Daesh militants who seized large swaths of Syria and Iraq in 2014. Since then, the IS has suffered major setbacks at the hands of the coalition, losing large chunks of the territory the militant group once held. The Syrian Kurdish forces, backed by the US-led coalition, are closing in on IS de facto capital, the city of Raqqa. "By this attack, Turkey is trying to undermine Raqqa operation, give (IS) time to reorganize and put in danger lives of thousands of" displaced, the YPG said on its Twitter account. — Agencies