Roads around security installations were closed in some parts of the capital and some international institutions were put on lockdown or evacuated
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.
The explosion took place near the embassy's main gate, where a Reuters journalist saw a scorched, damaged motorbike and a damaged police vehicle lying amid debris as police gathered around and a helicopter whirled overhead.
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 that one policeman was killed.
"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.
Last summer, Islamic State said it was behind militant blasts that struck the capital over the course of a week, including one near the French Embassy that killed a policeman.
Tunisia's critical tourism sector is highly vulnerable to militant incidents and was devastated after two major attacks in 2015 which killed scores of visitors at a beach resort and a popular museum.
Diplomats who have worked with Tunisia on its security capacity say it has grown more effective in preventing and responding to militant attacks in recent years.