Dakar -Faced with a growing jihadist threat, West African nations are scrambling to boost security but are seeing visitor numbers fall as foreign governments warn their nationals about the risks.
"The alert is being taken very seriously," said a Senegalese security source after police carried out a weekend of security operations in a bid to tackle the "terrorist threat".
Some 900 people were detained, mainly for security checks.
The situation is being taken particularly seriously in Dakar's Corniche district, which is home to many hotels, he said.
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Hotel security has been stepped up after 30 people were killed earlier this month in a deadly attack on a top Burkina Faso hotel and a nearby restaurant in the capital Ouagadougou.
Senegal is "an island of stability in an ocean of instability," said Bakary Sambe, researcher on religious radicalism at Gaston Berger University, referring to the unrest gripping Mali to the east and Nigeria further south where the Boko Haram jihadists are active.
"It is increasingly a strategic retreat area for western organisations" and occupies a "privileged position" in the region, he said.
That, however, is now making it an attractive target for destructive forces, "a symbolic target, because in attacking Senegal, you hit many interests," he said.
Mohamed Fall Oumere, security expert and director of the Mauritanian newspaper La Tribune, said he expects Islamist attacks to extend westwards to countries such as Senegal, Ivory Coast and Mauritania which have hitherto been largely spared "because of the security noose" around the area.
'Allies of the Crusaders'
The jihadists want to send three messages, Oumere says.
One is to France, telling them that their 2013 intervention in Mali "remains unresolved" while another is to France's allies to warn them that "they are still in the firing line," he said.
The third is a message to the Islamic State group, a competing jihadist faction, "which will unfortunately result in much damage and bloodshed," he said.
Northern Mali fell under the control of jihadist groups linked to Al-Qaeda in 2012.
They were largely ousted by a French-led military operation launched in January 2013, although large swathes of the area remain lawless and prone to attacks.
In an interview with Mauritania's Al-Akhbar website, a leader of the Al-Qaeda Islamic Maghreb (AQIM) group threatened allies of the Western "crusaders" in reference to Burkina Faso, Chad, Niger, Senegal and Togo.
Troops from the five countries make up most of the UN forces in Mali, and some of these nations host US and French military bases on their soil.
"We say to all those countries in the region which are allied to France and which participate in this Crusader war against Umma (the Islamic community) that we will spare no effort to strike them, and the Western interests they house," Yahya Abou El Hamame said.
Speaking to AFP, French security expert Yves Trotignon, who knows the region well, said Niger seems very vulnerable and that mounting an attack on the capital Niamey "wouldn't be very difficult".
'Avoid crowded areas'
Last week, Niger's Interior Minister Hassoumi Massaoudou spoke for the first time of arrests over the past month of people who came to Niamey intending to carry out the kind of attacks seen in Ouagadougou.
"We receive information and threats around every two months," he told the French broadcaster RFI.
In Dakar and Abidjan, the US and French envoys have urged their nationals to "avoid crowded areas" as they did after the November 20 attacks on a hotel in the Malian capital Bamako, which killed 20, 14 of them foreigners.
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Even in Sierra Leone, where the Ebola virus has hit the tourist sector and where authorities lend little credibility to threats of attacks against hotels, security is being beefed up around major buildings, according to hotel sources.
Last week Idriss Deby Itno, president of Chad -- a key member of France's counter-terrorism mission in the Sahel region -- said terrorism had become a worse threat than Ebola, which has killed over 11,000 people.
During a recently solidarity visit to Burkina Faso, he described terror as "an epidemic, worse than Ebola, worse than any illness."
The Chadian leader said it imposed an additional burden on poorer countries that already had enough problems to deal with.
"With the meagre means available to us in this region, you cannot combat terrorism while also thinking about development, about youth employment, about creating jobs," he said.