ISTANBUL — A Syrian activist and her daughter, a journalist, have been found murdered in their apartment in Istanbul, family and friends reported on social media Friday.

The activist, Orouba Barakat, 60, and her daughter, Halla Barakat, 22, were discovered Thursday night in Uskudar, on the Asian side of the city. The news was first announced on social media by Shaza Barakat, the elder Ms. Barakat’s sister. The two women had been stabbed to death, the Turkish news agency Anadalou reported, quoting a police official.

The Barakats came from a large family known for its long opposition to President Bashar al-Assad of Syria and his predecessor and father, Hafez al-Assad. The two women were both active in the Syrian refugee community in Turkey.

The elder Ms. Barakat was a member of the opposition Syrian National Council, now known as the Syrian National Coalition, but she had also criticized some members of the opposition. Halla Barakat was an editor for Orient TV, which covers events in the Middle East, and had also worked for the Turkish Radio and Television Corporation.