When a radical French Muslim cleric was arrested in Mali last month on his way to join Islamist rebels in the north, people in neighbouring Senegal were quick to notice a key detail. He was carrying fake Senegalese identity papers.
It heightened the worst fears of Mali's western neighbour: the spectre of terrorism spreading across the border into one of Africa's most peaceful countries.
Senegal and other neighbours might have to confront their fears soon. The United Nations Security Council voted on Thursday to approve a military intervention in Mali, led by African forces and backed by Western military trainers.
The intervention, aimed at recapturing the north from the rebels who seized it this year, could have unintended consequences – including a possible spread of violence in the region.
The Islamists in northern Mali, with strong links to al-Qaeda, have already threatened to bomb the capitals of any African nation that contributes troops to the planned military force.
With porous frontiers and corrupt border guards, the radicals in northern Mali could easily move across the borders. Some Senegalese volunteers have joined one of the leading Islamist rebel groups, al-Qaeda in the Islamic Maghreb, which has kidnapped dozens of Europeans and Canadians. And AQIM has reportedly used Senegal for some of its money-laundering operations.
This fear of spreading terrorism is a key reason for the Security Council's decision to approve the force of 3,300 troops, which is likely to enter Mali next year to train the army and help it retake the north. The force aims to push back the jihadists before they can cross borders into other countries.
"If we don't stop them, it will spread through the whole region," Abdou Lo, a political analyst in Dakar, said recently.
But that same threat of expanding terrorism is also a cause of anxiety and hesitation among many African nations as the intervention looms. Recent kidnappings in previously safe places in Niger and southern Mali have shown that Mali's radical militias can roam widely.
Senegal is likely to contribute troops to the force that enters Mali next year – although probably fewer than Nigeria, Burkina Faso and Niger, the most directly affected neighbours. Senegal could also serve as a communications and logistics hub for the international force, since it has the best seaports and communications technology in the region. It also has French military bases and 300 French soldiers, and it has played host to the U.S. military in African counterterrorism exercises.
Yet this strategic role could make it a target for reprisals by the Islamist militants. "The government is quite cautious," said a former presidential adviser in Senegal, speaking on condition of anonymity.
"There are dormant terrorist networks in Senegal that could make their presence felt," he said. "The military intervention in Mali would be very risky. It's a huge territory, it wouldn't be a conventional war, it would cost a lot, and the people are very mobile. Is it better to talk the rebels out?"
Mali's authorities are convinced that the Islamist radicals will seek targets in neighbouring countries. "Their target is Western civilization," said Fadiala Sidibe, police commissioner in Mopti, near the rebel-controlled territory.
"They will try to take Europeans hostage. They will bomb vehicles. They want to impose Islamic sharia law all over West Africa."
While the planned military intervention will heighten the risks for the region, it could also worsen the humanitarian crisis in northern Mali.
The rebel takeover of the north has already forced nearly 500,000 people to flee their homes or become refugees in neighbouring countries, and a new confidential UN report has warned that another 400,000 people could be pushed out of their homes if there is military intervention in the north.
"No clear plan exists to ensure that a military intervention would not exacerbate the already disastrous humanitarian situation," said Alexandra Gheciu, a University of Ottawa professor who specializes in international security.
Peter Maurer, president of the International Committee of the Red Cross, has warned that the military intervention would have a high humanitarian cost that has been largely ignored so far.