They were in Idlib province near the Turkish border, according to the Syrian Observatory for Human Rights.

BBC: US woman Nicole Mansfield killed fighting in Syria

Elsewhere, Syrian security forces purportedly "seized" explosive, weapons and ammunition in Homs and in Idlib province.

CNN: STORY HIGHLIGHTS

They were filming a documentary about Syrians fleeing to Turkey and were staying with activists in Idlib province.

CNN: Syria cracking down on journalists, activists say

Activists in the city of Maaret Nouman in Idlib province reported that a group of U.N. observers arrived "suddenly" on Friday and met with residents there.

CNN: SHARE THIS

Joshua Landis, director of the Center for Middle East Studies and associate professor of Middle Eastern studies at the University of Oklahoma, said Alawites live "cheek by jowl" near Sunnis in Homs, Hama and Idlib province in the west.

CNN: SHARE THIS

But Turkish authorities said Sunday they had detained nine Turkish citizens with links to the Syrian intelligence agency in connection with the bombings in the border town of Reyhanli, a hub for Syrian refugees and rebels just across from Syria's Idlib province.

NPR: Turkey Says It Won't Be Drawn Into Syria Conflict

Olivier Voisin, 38, died in a hospital in the city of Antakya in Turkey where he had been treated for injuries sustained in the Syrian province of Idlib on 21 February.

UNESCO: MEDIA SERVICES