A French delegate to a conference of socialists in Lebanon has said he was detained by gunmen linked to the Islamist movement Hezbollah.
Karim Pakzad said he was held for four hours after being stopped while taking photographs from an open-top car in an area known as a Hezbollah stronghold.
France described the incident as "totally unacceptable".
Hezbollah said the two were released after it had made sure Mr Pakzad and his companion were not Israelis.
Mr Pakzad, who was representing the French Socialist Party at the two-day Socialist International conference in Beirut, said he had been taking pictures of a mosque with a friend when he was approached by armed men.
He said he was blindfolded and taken to an unidentified location where he was held in isolation and his cell phone, wallet and medicine were taken away.
Hezbollah said Mr Pakzad's photographic activities had "aroused suspicion" and that the two men were treated with "respect".
"Once we were sure that the Frenchman and his companion were not Israelis we had no problems" with them, the group said in a statement.
The French foreign ministry protested against the incident.
"We count on the diligence of Lebanese authorities, responsible for the investigation and judicial follow-up of this incident," a ministry statement said, adding that Pakzad had filed a formal complaint.
Hezbollah - or the Party of God - is a powerful political and military organisation of Shia Muslims in Lebanon.
Observers say its concerns over security have increased since its 2006 war with Israel.
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