Another foreign fighter, British national Anna Campbell, was killed in the ranks of the PKK-affiliated groups in Syria on March 15 as result of a Turkish airstrike, her father confirmed yesterday.

Dirk Campbell, the father of the killed Briton, said to the BBC that his daughter was fighting against the Turkish Armed Forces (TSK) and the Free Syrian Army (FSA) in Afrin for the Women's Protection Units (YPJ), the women branch of the PKK's Syrian-affiliated People's Protection Units (YPG), when killed by an airstrike. The PKK is recognized as a terrorist organization by the U.K., along with Turkey, the U.S. and the EU. However, its affiliations are not thought as a terrorist group by those countries except Turkey, despite evidence that proves strong links between them.

It was reported that Campbell, 26, was a plumber and lived in East Sussex, southwestern U.K., before joining the terrorist group. Campbell's father said he tried to make her return to the U.K. many times but failed to do so.

While the number of British nationals killed in the ranks of the YPG has increased to eight, Campbell became the first woman among them.

In January, Alistair Burt, the U.K. minister of state for the Middle East, acknowledged that Britain is aware of the possible links between the PKK terrorist organization and the YPG, saying at a session of the House of Commons' Foreign Affairs Committee: "We are very concerned over possible links. We don't seek any link with the PKK and ourselves in any way."

The U.K. government previously called on its citizens to not travel to Syria, warning that they may face being arrested and face a trial when returning to the U.K.