Sana'a, Yemen  - Yemeni authorities are considering "all possibilities" as they try to find the kidnappers still holding six foreigners hostage in the north-western part of the country, Interior Minister Mutahar Rashad al-Masri said Saturday.

"We are considering all possibilities," the minister told reporters.

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

Three days later, the bullet-riddled bodies of the two German women and the South Korean woman 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.

Al-Masri reiterated accusations pointing to the al-Houthi Shiite rebel group for the kidnapping, a charge the group vehemently denies.

"Who is the beneficiary of such a terrorist act, they are the Houthis, who want to harm Yemen's image," al-Masri said, while adding, "though all possibilities are open."

He said if al-Houthis were not the perpetrators, "they must have provided the kidnappers with assistance."

"Whoever they are, those criminals will not go unpunished," he said.

The minister said that further details on the case could not be provided as the search was still going on for the six hostages whose fate remained unclear.

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.

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

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

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 the al-Houthi group.(dpa)