Updated

Tribesmen kidnapped a German aid worker and her parents in southern Yemen on Monday and were holding them hostage, demanding the government release imprisoned clan members, Yemeni officials and a tribe leader said.

The aid worker, who is based in Yemen, and her visiting mother and father were snatched by Bani Dhabyan tribesmen in Dhamar province, located about 100 kilometers (65 miles) south of the capital, San'a, a Yemeni security official said.

A Bani Dhabyan clan leader confirmed members of his tribe had kidnapped the Germans and warned the government against using force to free them. He said the Germans were the tribe's "guests" and would not be harmed.

The clan leader spoke to The Associated Press by telephone but would not give his name, fearing government reprisals. He would not provide further details but said he was not directly involved in the kidnapping and was trying to mediate.

The security official said the kidnappers were demanding the release of two tribesmen detained four months ago in connection with another kidnapping case.

The government sent troops to the area and detained several tribesmen for questioning, said the official, who spoke on condition of anonymity because he was not authorized to talk to the media.

In Berlin, German Foreign Ministry spokesman Jens Ploetner said the three Germans were missing, and "we must assume based on current information that the three were kidnapped." He said Berlin was "working to clarify the situation" but would give no further details.

The German and Yemeni officials did not identify the captives.

Tribesmen in Yemen frequently take foreign tourists hostage to pressure the government on a range of demands, from freeing jailed clan members to improving roads, hospitals and schools in their area. In the majority of cases, the hostages are freed unharmed.