Christians Under Attack

Yet MEC, which works in the region, added that despite the withdrawal of Western investigators "a few of those close to this situation remain hopeful before God that those still missing are alive and will be released one day."

Christian aid worker Johannes Hentschel, his wife Sabine and their young children Lydia, Anna, Simon, and married British engineer Anthony Saunders were among nine foreigners abducted in 2008 during an outing in the north-western Yemeni province of Saada.

Last year Anna Hentschel, 3, and Lydia Hentschel, 5, were rescued in an operation involving security forces from neighboring Saudi Arabia in the province's Shada district, officials said at the time.

However the bodies of three other abducted Christians, German Bible students Rita Stumpp, 26, Anita Gruenwald, 24, and South Korean teacher, Eom Young Sun, 33, were found murdered.

WHEREABOUTS UNKNOWN

There has been no news about the whereabouts of the rescued girls' parents, their small brother Simon and the British engineer, Christians familiar with the case and investigators said.

Some Yemeni officials attributed the kidnappings and murders to forces linked to the al-Qaida terror group and rebels. The adult Christians were working at the Protestant-run Al Jumhuri hospital in Saada, Yemen.

Since the mid 1990s at least 200 foreigners are known to have been kidnapped in Yemen. In most cases, they were set free after ransom payments, but observers have suggested that the Christians have been held for religious reasons.

MEC told Worthy News that against all odds, its contacts "are hopeful that current events in Yemen, whilst disturbing in themselves, may lead to information about the missing four becoming available."

MASS PROTESTS

Yemen is currently engulfed in mass protests calling for autocratic President Ali Abdullah Saleh's ouster which activists hope will lead to more openness and freedom.

MEC said that amid the turmoil, Yemeni Christians have been praying that "The missing four [Christians], assuming they are alive, will know the peace, presence and daily provision of Jesus and will be released unharmed shortly."

They also urged fellow believers around the world to pray for "All expatriate Christians working in Yemen" that they "will know the Lord's guiding and protection," MEC added.

The kidnappings have reportedly added to concerns among foreign Christian aid workers about their safety in the country of roughly 23 million people, although mission work continues. (With reporting by Worthy News' Stefan J. Bos).