Tunisia has announced it is closing its land border with war-torn Libya for 15 days after a deadly bus bombing killed at least 13 people on a presidential guard bus in Tunis
The National Security Council, headed by President Beji Caid Essebsi, decided to close the frontier from midnight on Wednesday with "reinforced surveillance of maritime borders and in airports", a statement said.
The bus was hit on the busy Mohamed 5 Boulevard on Tuesday evening, prompting Essebsi to impose a nationwide state of emergency.
The Islamic State of Iraq and the Levant (ISIL) claimed responsibility for the attack in a statement shared on its supporters' social media accounts on Wednesday.
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In addition to temporarily closing its Libya border crossing, Tunisia will hire 6,000 more recruits for security forces and act to protect itself against Tunisians returning from conflict zones like Syria, the president's office said.
Tuesday's incident was the third major attack in Tunisia this year following the gun assaults on a Sousse resort hotel in June and the Bardo National Museum in Tunis in March.
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"According to the preliminary details, the attacker was wearing a bag on his back," Hichem Gharbi, a presidential security official, told local Shems FM radio.
"He had on a coat and was wearing headphones. He blew himself up just getting into the door of the bus with military explosives."
It was the first suicide bombing in Tunis.
In October 2013, a bomber blew himself up on a beach in Sousse, while an al-Qaeda suicide bomber attacked the synagogue in Djerba, killing 21 people.
"This is an evolution in the behaviour of the terrorists," said Habib Essid, Tunisian prime minister, after an emergency security meeting.
"This time they attacked a symbol of the state and in the heart of the capital."
Troops and armed police patrolled the streets and set up checkpoints searching vehicles and pedestrians.
At Tunis International Airport, security forces were allowing in only passengers who were travelling.
Aymen Abderrahman, a local journalist, said that "hundreds of police and military" swarmed the area of the attack after the explosion.
"It's in the heart of downtown - a residential area," he told Al Jazeera by phone from Tunis, adding that people gathered and were "crying because it's the first time it's happened in downtown ever".
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"The blast was heard throughout the city."
The presidential guard is an elite security force that protects only the president.
Armed groups have targeted Tunisian security forces and civilians in the past, including in the capital and in areas in the country's central region and on the border with Algeria.
Earlier this week, the interior ministry said that Moncef Marzouki, the former president, was the target of an assassination plot.
Marzouki "was informed by the interior ministry that he had been targeted in an assassination plan", a ministry spokesman told AFP, adding that it was planned by a "terrorist" group.
Source: Al Jazeera and agencies