"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.
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.
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"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.
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 Islamist 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 but 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.