Yemen's security situation has been deteriorating over recent years
Fears are growing for the safety of six foreigners abducted in Yemen at the weekend, after the bodies of three foreigners were recovered from the remote mountain area near the Saudi border where they were seized.
The missing are thought to include a British engineer and five Germans. The bodies of two German nurses and a South Korean teacher were flown to the capital Sanaa on Tuesday.
Since 2004, this border region has endured sporadic civil war between Yemeni security forces and local rebels, and media access is tightly restricted.
But the kidnap and murder of foreigners appears to mark a new phase in the pattern of violence.
Local rebels in the Saada region have not taken foreign hostages before, and they deny any involvement in the kidnapping.
However, the Saada conflict has become so complex since its inception that it is hard to distinguish with clarity and confidence all the overlapping, shifting links between the different actors in play.
Yemeni tribes have a long history of kidnapping foreigners to extract concessions from the central government but these "bargaining chips" are almost always released unharmed.
Four Western hostages were killed in a bungled rescue attempt by security services southern Yemen in 1998, but this incident stood apart from a normal tribal kidnap.
The London cleric Abu Hamza is still to stand trial in the United States for his alleged involvement in this incident, while his son and stepson were both jailed in Yemen for their part in the plot.
Al-Qaeda and its affiliates remain likely suspects, as they have been held responsible for the deaths of 14 tourists in the last two years.
Spanish, Belgian and South Korean nationals have died in suicide attacks and gunfire on tourist groups in the eastern desert province.
But the calculated execution of captive hostages - as now appears to be the case - represents a new and chilling tactic. If al-Qaeda claim responsibility for these deaths, it will confirm fears that the organisation's capacity and ambition in Yemen are increasing.
Yemen is struggling to provide for its population's basic needs
In January 2009, al-Qaeda's branches in Saudi Arabia and Yemen merged to create a single transnational organization: al-Qaeda in the Arabian Peninsula.
Following this move, US Director of National Intelligence Dennis C Blair stated that Yemen was "re-emerging as a jihadist battleground and potential regional base of operations for al Qaeda".
Saudi national and former Guantanamo detainee Said Al Shihri operates from Yemen as al-Qaeda's deputy commander, and Saudi officials now name Yemen as their number one threat to internal security.
Yemen is a fragile state and the only low-income country in the Arabian peninsula.
Its oil sector provides 90% of export earnings and 75% of government revenue but oil production has passed its peak and output is declining.
The Yemeni government's ability to meet to the population's basic needs and respond to mounting political tension is diminishing as the economic strain increases.
With secessionist protests on the streets of south Yemen, resurgent terrorist activity and erratic bouts of fighting in Saada, the security situation in Yemen has deteriorated sharply in recent years.
Three years ago, few people were predicting that events would unfold in such a tragic way.
In 2006, then British Ambassador Mike Gifford said: "What Yemen needs is someone like Michael Palin to come and do a television programme on the country."
Now, the Foreign Office advises against all but essential travel to Yemen due to the threat of terrorism and tribal violence.
The nine hostages were professionals and aid workers, not tourists, who had bravely elected to operate in a ceasefire zone.
Yemen is now offering a $250,000 (£150,000) reward for information leading to the capture of the kidnappers.
Ginny Hill is the author of Yemen: Fear of Failure, a Chatham House briefing paper