Tunisian media are reporting that two people on a motorcycle set off a blast near the US Embassy in the Tunisian capital, Tunis.
The private Radio Mosaique said it was a suicide attack and reported that five police officers were wounded in the explosion Friday. That report could not be immediately confirmed.
The station, which is usually reliable, said the two approached the police patrol as if to seek information before setting off an explosive device.
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.
Islamic extremists have targeted Tunisia in recent years, killing scores of people.