A high-ranking German diplomat and his family are missing, feared kidnapped, in eastern Yemen.
Juergen Chrobog is a former ambassador to the US
Juergen Chrobog, 65, is a former deputy foreign minister and former ambassador to the US.
He has gone missing with his wife and three children, a foreign ministry official said.
Last week two Austrian tourists were kidnapped, and later freed, by Yemeni tribesmen who had been demanding the release of their relatives from prison.
The German foreign ministry confirmed their former colleague was missing.
Mr Chrobog is now the chairman of a business foundation linked to car-maker BMW.
Spokesman Martin Jaeger said the family were on an organised tour, "travelling in a group, in which one vehicle fell behind".
The group had reportedly been travelling between the region of Shabwa and the southern port city of Aden.
"The foreign office is in contact with all the relevant authorities and is trying to find out where this family could be," he added.
"We will make every effort to bring this family to safety as quickly as possible."
'They are safe'
The Reuters news agency said it had spoken to one of the kidnappers.
"The hostages are safe. Their life is not in danger and they are the guests of our tribe," a member of the al-Abdullah tribe reportedly told Reuters by phone.
"We were forced to do this to focus the government's attention to our cause," he said.
He said the kidnappers wanted the Yemeni government to release five of his tribesmen, who are in jail for criminal charges including murder.
Foreigners have often been kidnapped by armed tribal groups trying to force some kind of concession out of the Yemeni government, but are usually released unharmed.
Last month two Swiss tourists were seized, and later released.
However, four Britons kidnapped in Yemen in 1998 died when they were used as human shields during a bungled rescue attempt by state troops.