A UN panel that advises the security council has called for internet and social media companies to respond to the exploitation of their services by al-Qaida and other extremist groups who use the web to recruit fighters and spout “increasingly horrific propaganda”.

The panel recommended in a report circulated on Wednesday that these companies brief the security council committee monitoring sanctions against al-Qaida, its affiliates and the Islamic State group on measures they are taking to prevent such misuse.

“A worrisome trend over the past year has been the growth of high-definition digital terror: the use of propaganda, primarily by [Islamic State] and its sympathisers, to spread fear and promote their distorted ideology,” the panel of experts monitoring sanctions against extremist groups and individuals said in its report to the security council.

It said the scale of digital activity linked to Isis, and to a lesser extent some al-Qaida affiliates, had strategic implications for how the threat from extremists would evolve in the coming years among the “diverse, dispersed … diaspora of foreign terrorist fighters”.

In recommending that internet and social media companies brief the sanctions committee, the panel said: “The scale of the digital threat linked to radicalisation, together with the need for concerted action on countering violent extremism, calls for further action by the security council”.

The internet’s impact on extremist groups is one facet highlighted in the report which covers the global threats posed by al-Qaida, its affiliates and Isis. Their actions have had an “enormous” human cost in recent months, it says, with major bombings, assassinations and exploitation of several million people in not only Iraq and Syria but also Afghanistan, Libya, Nigeria, Somalia and Yemen.

The panel said al-Qaida remained overshadowed by the attention paid to its splinter, the Islamic State group, which controls large swaths of Syria and Iraq. The grip of al-Qaida leader Ayman al-Zawahiri on affiliates appeared to be weakening, it said, and al-Qaida’s financial position remained precarious compared with that of Islamic State, which “can claim to have achieved what al-Qaida never did: the building of a territorial entity through terrorist violence”.

But al-Qaida and its affiliates still posed a serious threat in many parts of the world, the panel said, becoming more visible and active in Afghanistan over the past six months, while associated groups had grown in number in south and central Asia, and al-Shabaab, its affiliate in Somalia, remaining a major security threat in the Horn of Africa.

Southern Libya remained “a safe haven” for extremists planning attacks in the Maghreb and Sahel regions, and the experts said they have been told of anti-aircraft guns and portable air defence systems in the hands of extremist groups.

Boko Haram had expanded deadly incursions into Cameroon, Chad and Niger but the panel said its ability to maintain long-term control over 20,000 square kilometres of north-eastern Nigeria “will require heavier weaponry, access to natural resources and some ability to sustain a local population”.

It said the Indonesia-based extremist network Jemaah Islamiyah appeared to be reviving and was recruiting professionals including engineers and information specialists, which could pose “a significant long-term threat” to south-east Asia.