Sana'a, Yemen  - Yemeni tribesmen freed a German oil expert and his Yemeni companions on Tuesday, two days after they kidnapped them in southern Yemen, Yemen's state news agency reported.

The agency quoted an Interior Ministry source as saying that the freed hostages were expected to arrive in the capital Sana'a late in the day.

A security source close to the negotiations with the kidnappers, however, told Deutsche Prsse-Agentur dpa that the hostages have not been handed over to the government.

Officials said earlier that the kidnappers had agreed to set the hostages free and they were expected to hand them over to a military official tonight.

The source said a breakthrough was reached in negotiations between the government and the kidnappers after the intervention of Yemeni President Ali Abdallah Saleh's half-brother and military commander Ali Mouhssien al-Ahmar.

Al-Ahmar made pledges to the abductors to discuss their demands in exchange for releasing the hostages, said the source, who asked not to be named.

Armed tribesmen kidnapped the German oil 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. (dpa)