Syrian activists say an opposition supporter who became an Islamic State militant has died in central Syria.

The Britain-based Syrian Observatory for Human Rights says Abu Bilal al-Homsi died earlier this week in the central province of Homs. He had kept in touch with journalists even after joining the IS.

The Observatory's chief Rami Abdurrahman said Friday it wasn't immediately clear whether al-Homsi died in an airstrike in the historic city of Palmyra or whether he carried out a suicide attack.

Homs-based activist Bebars Al-Talawy says al-Homsi most likely carried out Monday's bombing in a government-held neighborhood in the city of Homs, when 19 people were killed and nearly 100 were wounded.

Al-Homsi, who was in his late 20s, left his hometown of Homs in mid-2014 and later joined IS.