The Taliban's reliance on extortion and kidnappings, along with narcotics and illegal mining operations, is transforming it from a group driven by religious ideology into a criminal enterprise, UN monitors say in an annual report.
It quotes Afghan security officials as estimating that the Taliban extracts about US$8 million a month from the southern province of Kandahar alone through drugs, extortion and illegal mining.
In neighbouring Helmand province, the country's main poppy-producing region, the May harvest could yield US$50 million "in the worst-case scenario", the report cited Afghan official estimates as saying.
Taliban revenue from illegally mined onyx marble is believed to be "significantly larger than US$10 million a year", it added.
The report says there are 25 to 30 illegal mining operations in southern Helmand, most of them close to the border with Pakistan, allowing onyx marble to be easily smuggled into the international market.
It said executing civilians and aid workers helps the Taliban assert its power, block security improvements and prevent economic development 13 years after it was ousted from power by a US invasion. It also creates new funding sources for the hardline Islamists, who are bent on toppling the Afghan government.
The group has acquired more sophisticated improvised-explosive devices since late last year, the report says. In January, authorities in Kandahar seized a suicide vest camouflaged as a leather jacket, which analysis showed would have been practically undetectable with metal detectors.
"Explosive material was woven into the threads of the padding of the jacket, making it also unrecognisable as a suicide vest during a physical body search," said the report by the UN Analytical Support and Sanctions Monitoring Team, a UN Security Council committee monitoring sanctions against the Taliban.
The report is likely to make grim reading for the United States, whose primary motivation in invading Afghanistan in 2001 was to wipe out the safe havens the Taliban afforded al-Qaeda after the 9/11 attacks.
It said al-Qaeda-linked networks pose a long-term security threat to the region and beyond despite this year's drawdown of Nato troops in Afghanistan.
Three al-Qaeda affiliates in Pakistan - the Pakistani Taliban, Lashkar-e-Taiba and Lashkar-e-Jhangvi - regularly took part in attacks on Afghan forces in eastern and southern Afghanistan, the report said. In the north, the Islamic Movement of Uzbekistan "continues to gather strength" among Afghans of Uzbek origin.
Afghan security forces in January twice reported the presence of Chechen fighters in Logar and Kabul provinces, and al-Qaeda affiliates are unlikely to leave Afghanistan in the near future.
"They present a worrying, long-term security threat emanating from Afghanistan into the region and beyond," with particular ramifications for South and Central Asia, the UN experts said.
The report described an increasingly divided insurgency, with new organisations making the security situation more volatile. Reports that more than 50 mid-level Taliban operatives were assassinated in January and February may be another sign of growing rivalry, it warned.
The committee submitted its report after members made five visits to Afghanistan and held extensive talks with the government and international forces.
Reuters, Agence France-Presse