TUNIS — Four Tunisian soldiers were killed and 11 others were wounded on Wednesday in an attack by suspected Islamist militants on a bus carrying soldiers in Kef near the Algerian border, the Defense Ministry said.

The attack came while Tunisia was preparing its first free presidential election on Nov. 23 and only ten days after parliamentary elections won by secular party Nida Tounes.

Tunisia has struggled to subdue hardline jihadis opposed to the transition to democracy following the revolt against former President Zine El Abidine Ben Ali. The military cracked down on militants in the run-up to the polls.

“Terrorists attacked a bus carrying military personnel …Four soldiers were killed and 11 others were wounded in the attack in Kef city,” ministry spokesman Belhassan Ouselati said.

Ouselati said the gunmen tried to climb onto the bus to kill all the soldiers, but the soldiers returned fire, prompting them to escape toward the mountains.

Among militant groups operating in Tunisia is Ansar al Sharia, which the United States considers a terrorist organization and accuses of orchestrating the storming of the U.S. embassy in Tunis in 2012. g