An explosion has been reported outside the US embassy in the Tunisian capital Tunis, the interior ministry said.
Witnesses said a man on a motorbike blew himself up near the diplomatic mission in the Berges du Lac district, causing panic among pedestrians at the site.
Photos posted on local news websites showed damaged vehicles on the road outside the embassy.
The local Radio Mosaique FM said that five police officers were wounded. That report could not be immediately verified.
Armed gunmen have targeted Tunisia in recent years, killing scores of people.