BEIRUT — In the first attack to target a campaign event, a mortar shell slammed into a tent packed with supporters of President Bashar Assad, killing 39 people and wounding 205 others, Syrian state TV said Friday. The shelling underscored deep fears in government strongholds that rebels will escalate attacks in an attempt to disrupt the balloting.

Assad is widely expected to win a third, seven-year mandate in the vote scheduled for June 3, but the West and opposition activists have criticized it as a farce since it is taking place despite a raging civil war.

The 49-year-old president himself has not made a public appearance in more than a month and was not at the gathering struck by the mortar shell late Thursday in the southern city of Daraa. But campaigning has begun in earnest, with supporters waving his pictures and Syrian flags during daily demonstrations in the capital, Damascus, the coastal city of Latakia and other government-held areas.

Many gatherings have been held in so-called “election tents” where nationalistic songs are played and supporters mingle.

State TV showed pictures of Assad supporters dancing in a campaign tent in Daraa. It then showed people lying dead and wounded on the ground, including several children.