Islamist militants fighting in Burkina Faso are on a campaign to expand their footprint in West Africa.

And seven sources, including Ghanaian security officials and diplomats, have told Reuters the fighters are discreetly using Ghana's north as a logistical and medical rear base.

Stocking up on food, fuel and even explosives, as well as getting injured fighters treated in hospital.

Burkina Faso has lost control of over half its territory as a pro-al Qaeda group known as JNIM have gained ground.

Clingendael, the Netherlands Institute of International Relations, said in a recent report Ghana appeared to have accepted a de facto non-aggression pact with JNIM, citing high-ranking government sources.

Experts say that risks letting militants put down roots in Ghana.

Here's Kars De Bruijne from the institute.

"And we did see a number of incidents where JNIM is, or JNIM associates are likely present in Ghana for some time, temporarily passing by, making procurements, sometimes trying to do recruitment. And so, that is really serving as a wake-up call."

Ghana holds elections on Dec. 7.

It is seen as a strong democracy and has a close relationship with the West.

"Ghana wants to really make sure that they can have their elections, that there are no attacks. They know, of course, of the risks that they have in Ghana and know what extremists are capable of, and they really want to prevent that.

"JNIM, at the same time, they're going to face, then, a really committed, really strong army, I'd say. And, I mean, they don't want to attack their own supply line and their safe haven."

Ghana shares a nearly 400-mile border with Burkina Faso.

The country is at the heart of an insurgency that has killed thousands and displaced millions.

Experts say the Sahel region is now the epicentre

of global terrorism as factions loyal to al Qaeda and Islamic State expand their presence.

A JNIM leader this week told French broadcaster RFI it was aiming to push into Ghana, Togo and Benin.

Unlike Benin and Togo, Ghana has not suffered a major attack.

Ghana's ambassador to Burkina Faso told Reuters the militants were taking advantage of porous borders.

He denied suggestions of a non-aggression pact with the jihadists and said Ghana was working with Burkina Faso to "flush them out."

Ghana's Information Ministry declined to comment.

Since Islamist militants emerged in West Africa 20 years ago, multiple countries, including Burkina Faso, have tried similar informal non-aggression pacts.

They all collapsed as the insurgency gained strength or governments fell with juntas expelling Western military support and turning to Russia for help instead.