Blast near US Embassy in Tunisia kills policeman

Two militants on a motorbike blew themselves up outside the US Embassy in Tunisia on Friday, killing a policeman and injuring several others in the country's most serious attack in months.

Media reports citing eyewitnesses said the attackers were on a motorbike. That report could not be immediately confirmed. 

Phones at the embassy went unanswered.

The Interior Ministry said two militants were killed carrying out the attack and five police officers were injured, while a civilian suffered minor injuries.

State news agency TAP reported one policeman was killed.

Police taped off the area around the blast site, which was littered with debris. The flag of the United States could be seen fluttering in the background.

"We heard a very powerful explosion ... we saw the remains of the terrorist lying on the ground after he went on the motorbike towards the police," said Amira, a shopkeeper.

Sirens could be heard on the major highway linking the Lac district, where the embassy is located, with Tunis and suburbs in the north. The US Embassy in a tweet urged people to avoid the area.

Roads around security installations were closed in some parts of the capital and some international institutions were put on lockdown or evacuated.

Photographs of the blast site posted on social media showed debris strewn around the area of a security checkpoint that controls access to the embassy, and damaged vehicles.

Dozens of people have been killed in multiple attacks by militants in Tunisia, notably in 2015 when the famed Bardo Museum outside the capital and a luxury beach hotel were attacked. 

The US Embassy, located in a residential area on the outskirts of Tunis, was attacked in 2012 by crowds angered by an anti-Muslim film produced in the United States. Since the fall of Tunisia's hard-line secular dictatorship in January 2011, Salafisim-driven militants have come into the open.