Fighters from a coalition of Islamist forces walk on March 29, 2015 in the Syrian city of Idlib (AFP Photo/Zein al-Rifai)

Islamist fighters on Monday kidnapped some 300 Kurdish civilians at a checkpoint in northwestern Syria, Kurdish officials and a local journalist told AFP.

It was not immediately clear which group was responsible for the kidnapping, though Kurdish officials accused Al-Qaeda’s affiliate Al-Nusra Front, which is active in Idlib province.

“A group of 300 people on five coaches and a mini-bus coming from Afrin were kidnapped at a checkpoint as they went to Aleppo to collect their salaries,” said Newaf Khalil, a spokesman for the Kurdish Democratic Union Party (PYD).

The kidnapping was confirmed by a second official from the PYD, the main Kurdish party in Syria, and a journalist in Afrin, who said the women in the group had been freed but the men and children taken.

“There were 300 people on five buses, and they were kidnapped in Dana, which is under the control of Islamist factions and Al-Nusra Front,” said journalist Ali Abdul Rahman.

The PYD officials accused Al-Nusra of being behind the kidnapping, but Abdul Rahman and the Syrian Observatory for Human Rights monitor said it remained unclear which group was responsible.

The Observatory reported similar details on the kidnapping, but said it was not immediately clear how many people were being held.

The Observatory said the captors had demanded, through the released women, that three men arrested by authorities in Afrin be freed.

There was no immediate confirmation of those demands from PYD officials or residents of Afrin, which is under Kurdish control.

The kidnapping occurred in northwestern Idlib province, where Al-Nusra and its allies wield considerable influence.

The Al-Qaeda affiliate helped capture the provincial capital Idlib city on March 28 along with a coalition of other opposition groups.

The incident is not the first mass kidnapping in Syria, where large groups of Kurds and Christians have been held, mostly by Al-Nusra’s extremist rival, the Islamic State group.

IS fighters are accused of kidnapping over 200 Assyrian Christians from Hasakeh province, and last year held more than 150 Kurdish schoolchildren kidnapped in Aleppo province.

Al-Nusra has also been implicated in kidnappings.

It has been accused of holding journalists and aid workers and in 2013 kidnapped a group of 13 nuns who were later released in a prisoner exchange.

More than 215,000 people have been killed in Syria since the conflict began in March 2011 with anti-regime protests that spiralled into a bloody civil war after a government crackdown.