"This kind of warfare is long term and there's no shortcuts to it. You've got to stay on course and it requires everybody cooperating. You can't underestimate their ability to resurge" General Donald Bolduc told reporters in Dakar.

Bolduc's comments late Monday came as the United States launched an annual military exercise dubbed Flintlock which will see 1700 special forces personnel from some 30 countries take part.

With jihadists in Africa increasingly resorting to attacks on markets and security forces the latest round of training would focus on improving police and military preparedness particularly for urban warfare.

"The most important training that we can do is connect that military training to the police" he said.

Despite losses in the battlefield extremists are becoming more "proactive" across the continent Bolduc warned.

"They have transferred tactics techniques and procedures particularly in improvised explosive devices and they have traded ideas and concepts on how to message and present themselves in public solidifying their ideology and what they stand for."

With Nigeria leading a regional offensive against Boko Haram's Islamist insurgency since last year the group has resorted to carrying out a string of suicide and bomb attacks in and around Africa's most populous country leaving thousands of civilians dead.

In Burkina Faso and Mali Al-Qaeda in the Islamic Maghreb (AQIM) claimed responsibility for deadly attacks on hotels popular with foreigners in November last year and on January 15 this year.

In east Africa Al-Qaeda-affiliated Shebab insurgents have lost ground since being routed from Mogadishu in 2011 but they continue to stage regular shooting and suicide attacks.

- IS 'reaching out' -

Bolduc said a key part of governments' fight against jihadists should be "countering the narrative" of extremists as their rhetoric is an essential part of their recruitment strategy.

He meanwhile warned that IS -- to which Boko Haram has pledged allegiance -- now poses a more direct threat than ever in Africa.

A US-led coalition has since 2014 been carrying out air strikes against IS targets in Iraq and Syria where the radical group holds large swathes of territory.

Now IS "is reaching out to Al Shebab it's reaching out to Boko Haram it's reaching out to AQIM. In some cases it's directly supporting AQIM. It's influencing Al Shebab it's influencing Boko Haram not directly supporting it but influencing it with its ideas" Bolduc said.

On Tuesday Nigeria's intelligence agency announced the arrest of a recruiter for IS who was preparing to go to Libya which has slid into chaos since the fall of Moamer Kadhafi in 2011.

Fears have been expressed about a link-up between IS fighters in Libya and Boko Haram as well as Al-Qaeda affiliated jihadist groups in places such as Mali and elsewhere in North Africa.

To date there has been little evidence of the use of foreign fighters in Boko Haram's insurgency which has left at least 17000 dead and displaced more than 2.6 million people since 2009.