Army and security forces surrounded on Tuesday a remote mountain village in southern Yemen where armed tribesmen are holding hostage a German oil expert and two local engineers, local security sources said.
The sources told Deutsche Presse-Agentur dpa that armoured personnel carriers and patrol vehicles laid siege to the Khubar Laqmoush village in the south-eastern province of Shabwa, dpa reported.
They said the forces were sent to the area to put pressure on the kidnappers to set the hostages free, and that authorities intend no solution by force for the crisis.
Armed tribesmen kidnapped the German expert and two Yemeni engineers on Sunday as they were heading to their work site near the Arabian Sea port of Balhaf in Shabwa, some 570 kilometres south east of Sana'a.
The abductors, who belong to the Laqmoush tribe are demanding the release of a jailed fellow tribesman accused of murdering a man from the same tribe in 1989.
Tribal sources said a team of provincial officials and tribal dignitaries began negotiations with the kidnappers late on Monday to secure the hostages' release.
Governor of Shabwa, Ali Hassan al-Ahmadi, told the Defence Minsitry's online newspaper that authorities were "exerting strenuous efforts to free the three hostages peacefully."
"The three engineers were not harmed and they are safe and sound," al-Ahmadi was quoted by the newspaper as saying.
He further expected that the hostages would be released "within the next few hours."
The German hostage works as a pipeline expert for Amecspie Hawk, a sub-contractor with Yemen LNG Ltd that runs the project.
Amecspie Hawk is building a 320-kilometre-long pipeline form the oil refinery in the north-central province of Mareb to the LNG exporting port of Balhaf.
The kidnapping is the third involving foreigners and the second involving German nationals in about a month.
On December 15, three Germans were captured in western Yemen. They were released four days later. On January 3, a South African mother and her two sons were seized by tribesmen in the southern province of Abyan. They were released a day later.
Disgruntled tribesmen from impoverished areas of Yemen often take hostages to use as bargaining chips to press the government for aid, jobs or the release of detained fellow clansmen.