SANAA, Dec 15 (Reuters) - Yemeni troops were encircling a mountainous area where armed tribesmen were holding three Germans hostage over a land dispute with another tribe, a provincial official said on Monday.

Troops coming from four directions were approaching the area 60 km (37 miles) east of the capital Sanaa where tribesmen were believed to be holding the Germans, one of whom works for the United Nations, Abdulmalek al-Gharbi, deputy governor of Sanaa province, told the ruling party's website (www.almotamar.net).

A security official earlier said the government has established contact with the tribe to secure the release of the hostages.

The U.N. employee and her visiting parents were on an excursion in the outskirts of Sanaa when they were seized by the armed tribesmen, the official told Reuters.

Besides pressing authorities over the land dispute, the kidnappers were demanding the release of two fellow tribesmen jailed for an earlier kidnapping, the official said.

The German foreign ministry confirmed the three were missing.

"Since yesterday afternoon, three Germans have been missing in Yemen. According to the information available to us, we must assume the three were abducted near Sanaa," a ministry spokesman told a news conference.

He said German officials were in contact with Yemeni authorities. He declined to give further details.

Disgruntled tribesman have often kidnapped Western tourists to demand better living conditions, schools and services in the Arabian Peninsula country, one of the poorest outside Africa.

Most have been released unharmed, but in 2000 a Norwegian diplomat was killed in a crossfire and in 1998 four Westerners were killed during a botched army attempt to free them from Islamist militants who had seized 16 tourists.

In January, two Belgian tourists were killed in an attack blamed on al Qaeda-linked militants who have launched frequent attacks on government and Western targets, including a U.S. warship and a French supertanker.

(Reporting by Mohammad Sudam; additional reporting by Kerstin Gehmlich in Berlin; writing by Firouz Sedarat; editing by Keith Weir)

AlertNet news is provided by