Sana'a, Yemen  - A Shiite rebel group in Yemen said Sunday it had gained "vital clues" that could help identify the kidnappers who are holding a German family and a British engineer in north-western Yemen.

Muhammad Abdul-Salam, a spokesman for the al-Houthi rebel group, told the German Press Agency dpa: "We have got vital clues that will help the search for the kidnappers and the hostages."

He said the group's leader Abdul-Malik al-Houthi, "would provide the information if he is asked to do so."

Abdul-Salam declined to provide further details.

A German family of five and the British engineer were taken at gunpoint along with two German theology female students and a South Korean female teacher while on a weekend excursion in the restive province of Saada on June 12.

Three days after the kidnapping, the bodies of the two German women and the South Korean teacher were found in Akwan in the Wadi Nushur area east of Saada. Wadi Nushur is close to al-Jawf province, where al-Qaeda and other terrorist groups have a presence.

The fate of the remaining six hostages has since remained unclear.

No tribal or political group has yet claimed responsibility or made demands.

Yemeni authorities have blamed the kidnapping on the al-Houthi group, a charge the group vehemently denies.

A massive search operation by the security and army forces, backed by thousands of tribesmen and ordinary people, is hindered by the ongoing conflict between government forces and al-Houthis.

Some of the hostages had been working for a local hospital in Saada, on the border with Saudi Arabia, some 240 kilometres north- west of the capital Sana'a.

On Saturday, Yemeni Interior Minister Mutahar Rashad al-Masri said the nine foreigners had ignored warnings by the country's authorities not to leave secure areas without security escorts.

"Five days before the kidnap, security bodies sent a warning to the German doctors that they should not move without a security escort," the minister said.

Kidnapping has been rampant in Yemen for nearly two decades. This time, however, the methods and the degree of brutality are different. (dpa)