The Islamist terrorist group known for kidnapping more than 250 Nigerian schoolgirls, has been active in conflicts in Mali, Central African Republic (CAR) and Syria, a spokesman for religious freedom said.

The spread of the militant group can be seen as evidence of cooperation with other militant groups, including al-Qaeda and Al-Shabaab.

All three groups are using conflicts in Africa and the Middle East as a training ground for jihadist fighters.

"There seems to be a tendency among Jihadi movements to use different crises as training grounds, " said team leader for Africa and the Middle East at Christian Solidarity Worldwide, Khataza Gondwe.

The Malian conflict is one example where Boko Haram activity was reported outside its usual territory in northern Nigeria, Niger and Cameroon.

Similar reports have come from CAR, where a least one UN official has claimed there has been a Boko Haram presence since 2013.

"There was a video in which Shekau [the leader of Boko Haram] said that they were coming to help their brethren," Dr Gondwe said.

"In the first attack on a church there, the people sheltering in the church said that the attackers spoke in English and said 'Open the door' before spraying the place with bullets," she added.

But beyond supporting their brethren and training recruits, the Syrian conflict has a theological appeal for Islamist terrorist groups.

Dr Gondwe said: "Now Muslims are moving to Syria – in some kind of eschatology, the final battle will happen in Jerusalem, so quite a few of them are heading that way."

Some Islamic teachings include end-time prophecies relating to Syria, or more particularly, to a broader region encompassing Jordan, Lebanon, Israel/Palestine and western Iraq.

One prophecy says that Jesus will descend from the white minaret at the Great Mosque in Damascus to fight the false messiah – an event which will speed the day of God's judgement.

Boko Haram, which means "Western education is sinful", became widely known for the abduction of schoolgirls from Chibok village, Borno province, Nigeria in April, prompting the #BringBackOurGirls campaign on social media.

Such raids on schools and villages are typical of the group's tactics. Dr Gondwe also suggested that Al-Shabaab had used similar techniques to Boko Haram in recent bombings in Kenya, targeting public places for maximum impact.

She said: "Boko Haram is able to amass and then attack an area that is insufficiently protected because the Nigerian army is stretched out. A surge of troops in that area is the only thing that will be able to combat it."

Nigerian President Goodluck Jonathan said in May this year that Boko Haram was responsible for the deaths of more than 12,000 people, and for injuring a further 8,000 since it began its insurgency in 2009.