Updated

An explosion has struck a southern Syrian town and there are conflicting reports on the cause of the blast. It's unclear if there are casualties.

The Britain-based Syrian Observatory for Human Rights says an Israeli warplane on Wednesday targeted a building in the southern town of Baath, on the edge of the Israeli-occupied Golan Heights.

The Observatory didn't say how it knew it was an Israeli warplane. Israeli warplanes and artillery have struck southern Syria in the past.

The Military Media of Lebanon's Hezbollah group claimed that the blast was caused by two rockets fired by members of al-Qaida's affiliate in Syrian, the Nusra Front.

Later, Hezbollah's Al-Manar TV said Syrian government troops retaliated, hitting a Nusra Front vehicle from which the rockets were fired.