Sahel and Sahara region is home to a tangled mix of social and economic problems which shift seamlessly across borders
The attack on the Algerian gas field has raised fears of the conflict in Mali becoming an international battle bleeding across the porous borders of the Sahel and Sahara region.
It also presents a major challenge to the military-dominated regime in Algiers – still in the shadow of a decade of bloody civil war – which had been accused of having an ambiguous stance towards the Mali crisis.
Algeria will now firmly be dragged into resolving the Mali conflict, while also dealing with the return of major action by Islamist groups on its home turf.
The hostage-taking has spelled out the complexities of the unrest in the Sahel: a tangled mix of communal tensions, economic struggle, desertification, poverty, criminality, kidnapping and smuggling, which shifts seamlessly across borders.
With six days of French airstrikes failing to erode the Islamist gains in Mali, French special forces prepared to launch a land assault on Wednesday around Diabaly, 250 miles (450 km) from the capital.
France's aim is to secure the vast desert area seized last year by an Islamist alliance, which combines al-Qaida in the Islamic Maghreb (AQIM) – the terrorist network's north African wing – with Mali's homegrown Movement for Oneness and Jihad in West Africa (Mojwa) and Ansar Dine rebel groups. But the Algerian hostage drama at the BP oilfield far away to the north at the Algerian-Libyan border marks a turning point and a widening of the game.
Attacks on oil-rich Algeria's hydrocarbon facilities are very rare, despite the country's decades of fighting an Islamist insurgency, mostly in the north.
Jon Marks, associate fellow at Chatham House, London's leading foreign affairs thinktank, said: "The attack is remarkable for a number of reasons.
"If you look at Algeria's conflict of the 1990s, out of which AQIM sprang, the major oil and gas fields of the deep south, a strategic interest to Europe, were not attacked. Even in Algeria's bloody history, this is the first time there has been major attack on a hydrocarbon facility.
"It shows the degree to which the events in Mali are an international Sahel and Sahara-wide issue. These groups are international: including Malians, people who came from the Libya conflict, but also from Algeria and Mauritania."
He said the attack showed how deep-rooted those groups were. "The groups we are now calling AQIM, that the French military are targeting, have roots going back decades in the region. They have been involved in cigarette smuggling, electronic goods smuggling, guns, drugs, a lot of criminality."
He described it as a potent "interface" where criminality meets politics in an area that is "more and more desperate".
Algeria, the region's economic and military powerhouse where the regime of generals holds firm despite the Arab spring elsewhere, had been a major opponent of foreign armed intervention in Mali, preferring negotiations.
Until now, it fiercely clung to its policy of non-intervention in its neighbours. But has now opened its airspace to the French air force, a historic event, and vowed to secure its vast desert border with Mali, an undertaking commentators say is almost impossible in the poorly patrolled desert wastes.
Although an ally of the US and France in fighting terrorism for years, Algeria has been accused by some of playing a double game in the Sahel where Islamist groups have flourished since the country's bloody war of independence. The regime's involvement in Mali and the Sahel will now become more of a focus, as the conflict looks likely to be drawn out.
A poll on Wednesday found 64% of French people felt the Mali intervention would increase the risk of a terrorist attack on French soil, and armed patrols were in force at potential targets such as the Eiffel Tower.
France had been acutely aware that hostage-taking in the Sahel would be the key immediate risk of its sudden Mali intervention.
Unlike Algerian terrorist operations in the 1990s, AQIM has never struck on French soil. But the militant groups that seized control of northern Mali last year had targeted foreigners for years on their own turf.
They already hold seven French hostages as well as four Algerian diplomats, seized several years ago. AQIM has made tens of millions of dollars from kidnapping Algerian businessmen or political figures for ransom, as well as foreigners.
On the same day that France launched its sudden Mali intervention last week, it staged a rescue attempt of a French intelligence agent held for more than three years by rebels in Somalia, and referred by the fake name of Denis Allex.
If the French rescue mission to save Allex was destined to deliver a warning against hostage-taking and head off reprisals against French hostages, the operation went spectacularly wrong. Two French soldiers died and the hostage was presumed to have been killed by his jailers during the failed assault.
The French president, François Hollande, was at pains once again on Wednesday to say France had "no interest" in Mali and was just "serving peace". Hollande emphasised his promise to break with murky post-colonial relations of the past.
Mali is small beer within the wider context of French economic interests in west Africa, but Mali's neighbours are a different matter. Niger's uranium services one third of the French nuclear power stations which produce most of the country's electricity.
It was in Niger that workers for French nuclear firm Areva were kidnapped in 2010, four are still held in the Sahel. Algeria – Africa's biggest country and France's biggest African economic partner – is a major exporter of oil and gas to Europe. The oil field hostage-taking shows the wider global interests that could now come into play.