Geneva, Jul 6 (IANS/AKI) : There are almost 30,000 foreign jihadists fighting in war-ravaged Syria and neighbouring Iraq currently, the head of the UN Security Council's counterterrorism agency said, warning that the risk of attacks in their home countries was growing.

"The number of foreign terrorist fighters is very high in Syria and Iraq," said Jean-Paul Laborde, UN assistant secretary general and head of its counter-terrorism Committee on Tuesday.

"There are nearly 30,000, and now that the territory held by Daesh (the Islamic State group) is shrinking in Iraq, we are seeing them return, not only to Europe but to all of their countries of origin, like Tunisia, Morocco," he told reporters in Geneva.

The figure is based on information compiled from governments, he said.

Attacks launched by foreign fighters returning to their home countries were likely to increase in ferocity, in retaliation for international military action that is putting them on the back foot, Laborde warned.

"The terrorist attacks in those countries of origin risk getting bigger and bigger to counter-balance the pressure on them" on the ground in Syria and Iraq, he said.

Another danger is that terrorist organisations like the Islamic State jihadist group have shown themselves able to adapt much faster and more flexibly than the governments fighting them, Laborde warned.

IS has shown a "remarkable ability to adapt" such as seeking new funding sources like drug smuggling, even as the territory it controls has been shrinking, he said.

The former French judge urged greater cooperation with internet giants like Google, Twitter and Microsoft to help track potential terrorists online and urged states to share more information faster.

"If we don’t do that, we will continue to see a growing number of terrorist acts," Laborde said.