Syrian soldiers prepare artillery to fire at positions of the Islamic State (IS) group in Syria's Qalamoun region, on Aug. 26, 2017. (Xinhua/Ammar Safarjalani)

MOSCOW, Nov. 7 (Xinhua) -- Russia's security heads warned Wednesday that the Islamic State (IS) and al-Qaida may merge and thus increase the threat of global terrorism.

"The transition to a network-based organizational model based on regional branches may push the IS leadership to merge with al-Qaida, which is also interested in replenishing its forces and means for conducting active terrorist activities," Secretary of the Russian Security Council Nikolai Patrushev was quoted as saying by TASS news agency.

"This will allow these two terrorist organizations to control the activities of their regional branches and affiliates more efficiently," he said at a meeting of foreign security services and law enforcement bodies in Moscow.

IS has lost most of the territories it occupied in Iraq and Syria, but it remains along with al-Qaida and its affiliates a potent threat, with a presence of both terrorist groups in various countries of the Middle East and Africa.

There are a number of signs indicating a possible convergence of IS and al-Qaida, Director of the Russian Federal Security Service (FSB) Alexander Bortnikov said at the meeting.

"Both international terrorist organizations use a close ideological base and common human resources to replenish each other's forces," Borthikov said.

Many terrorists, despite the armed clashes between al-Qaida and IS, are moving from one terrorist structure to another, motivated by personal gain, changes on the battlefield and other reasons, he said.

According to the Security Council's Patrushev, currently there are more than 200 terrorist groups in the world, of which IS and al-Qaida are the largest.

An inevitable defeat of terrorism in Syria and Iraq has forced foreign mercenaries to leave, return to their own countries, or create new centers of instability, he said.

According to Patrushev, the militants have changed tactics by joining local radical groups and criminal circles, forming criminal groups within national communities and diasporas of the world, as well as creating so-called "dormant cells," recruiting new members and accumulating financial assets.