In a report to the U.N. Security Council, Ban said the number of violent incidents rose from an average of 425 per month in 2006. The number of suicide attacks jumped to 160 attacks in 2007 from 123 in 2006 with 68 attempts thwarted in 2007 compared with 17 in 2006, he said.
While the insurgency draws strength from some Afghans, the secretary-general said, "the support of foreign-based networks in providing leadership, planning, training, funding and equipment clearly remains crucial to its viability."
Insurgent violence in Afghanistan is at its highest level since U.S. forces invaded the country in 2001 to oust the hard-line Islamic Taliban rulers, who harbored al Qaeda leaders blamed for planning the attacks in the United States on Sept. 11, 2001.
The focus of the violence has been in Afghanistan's southern and eastern provinces, but the insurgents are increasingly using Iraq-style tactics, such as roadside bombs, suicide attacks and kidnappings to hit foreign and Afghan targets around the country.
"Afghanistan remains roughly divided between the generally more stable west and north, where security problems are linked to factionalism and criminality, and the south and east characterized by an increasingly coordinated insurgency," the secretary-general said.
"In fact, even within the south, conflict has been concentrated in a fairly small area: 70 percent of security incidents occurred in 10 percent (40) of Afghanistan's districts, home to 6 percent of the country's population," Ban said.
But the secretary-general cited worrying trends the gradual emergence of insurgent activity in the previously calm northwest as well as the encroachment of insurgents into two provinces bordering Kabul, Logar and Wardak.
He said the tactics of anti-government elements changed noticeably in 2007 in response to the superiority of Afghan and international security forces in conventional battles.
The opposition groups were forced "to adopt small-scale, asymmetric tactics aimed largely at the Afghan National Security Forces and, in some cases, civilians: improvised explosive devices, suicide attacks, assassinations and abductions," Ban said.
"Of the over 8,000 conflict-related fatalities in 2007," he said, "over 1,500 were civilians."
Ban also expressed concern at the increase in attacks on Afghan and international humanitarian workers.
In over 130 attacks against humanitarian programs last year, 40 aid workers were killed and 89 abducted, of whom seven were later killed by their captors, Ban said. In addition, in 2007, over 40 convoys delivering food aid for the World Food Program were attacked and looted.
He noted that the Afghan National Army has more than 49,000 troops, compared to the 80,000 target, and is being forced to fight the insurgency as it builds its strength.
In terms of professionalism and performance, Ban said, the Afghan National Police force continues to lag behind the army, noting that a head count in August and September "uncovered major discrepancies between the actual number of its personnel on the ground and those on the payroll."
Ban said coordination between the Afghan security forces and NATO's International Security Assistance Force, known as ISAF, has improved.
But he said that while the 41,700-strong ISAF conducted several successful operations in unstable areas and continues to provide valuable assistance to provincial reconstruction teams, "its effectiveness is hampered by insufficient troop strength and by national caveats limiting the functions of some troops."
"In 2008 an important rebalancing of responsibility will be required between ISAF and the Afghan national security forces in respect of leadership and primacy in the security field, as the latter become more capable," the secretary-general said.
Ban recommended that the mandate for the U.N. mission in Afghanistan, which expires on March 23, be extended for a year. Ban reiterated that the guiding principle of its activities "is to reinforce Afghan leadership and strengthen international cohesion in support of that leadership."