Libya has postponed independence day celebrations and declared three days of mourning after a suicide bombing at an army checkpoint killed 13 soldiers.

Sunday's attack at Barsis, some 50km from eastern city of Benghazi, was the latest episode of violence to rock city, the birthplace of Libya's 2011 uprising, two years after the end of the civil war that toppled long-time leader Muammar Gaddafi.

The attacker blew himself up at a road checkpoint near the small military base killing 13 people and wounding three, state news agency Lana said.

Two of the wounded were in serious condition, the agency said. Two people were still missing.

Aymen al-Abdlay, a Benghazi army officer, said the blast happened after a truck parked at the checkpoint.

"There was a young man driving, but when the army troops went to check it out, the vehicle exploded," Abdlay said.

The attack left body parts strewn around the area, police officer Moetez al-Agouri said.

Intelligence chief assassinated

One witness said the blast left a sizeable crater in the ground.

The security post's chief, Fraj al-Abdelli, who was wounded in the attack, said the checkpoint had received several threats since arresting four people in November who were carrying weapons, explosives, money and a hit list.

The government postponed celebrations for Libya's independence day on December 24 and declared three days of mourning for the victims of what it called a "cowardly terrorist act," Lana said.

No group claimed responsibility for the attack, but the group Ansar al-Sharia fought last month soldiers who drove fighters from Benghazi.

The incident on Sunday comes just days after Colonel Fethallah al-Gaziri, the newly appointed chief of military intelligence in Benghazi, was assassinated during a visit to his family in the city of Derna.

Libya has witnessed a string of assassinations and bombings since 2011, but a suicide bombing marks a shift in tactics.

The security situation in Benghazi has sharply deteriorated in the past few months, prompting many countries to close their consulates there.

Source: Al Jazeera and agencies