Tunisian President Beji Caid Essebsi declared a national state of emergency Tuesday after a bus carrying members of the presidential guard in capital city Tunis exploded, killing 12 people and leaving 16 others injured.

Although no one has claimed responsibility for the incident, government officials confirmed the explosion was not due to a mechanical issue, but was an attack by terrorists.

"I want to reassure the Tunisian people that we will vanquish terrorism," Essebsi said on national television Tuesday evening.

The country's Islamic party, Ennahda, denounced the attacks, noting Tunisia was targeted because "it is a democracy and represents a model of moderate Islam."

The attack on the president's security team comes one week after an increase in local law enforcement. The government has not shared its reason for heightening security.

The country will remain in a state of emergency for 30 days.