KABUL, Afghanistan - The United Nations reported Saturday that insurgent violence has risen sharply in Afghanistan over the last three months, with roadside bombings, complex suicide attacks and assassinations soaring over last year's levels.

The three-month report by U.N. Secretary-General Ban Ki-moon to the U.N. Security Council appeared at odds with Pentagon assertions of slow but steady progress in Afghanistan - an assessment that was challenged by U.S. lawmakers during recent hearings on Capitol Hill.

In the report, Ban said the overall security situation in Afghanistan has not improved since his last report in March and instead the number of violent incidents had "increased significantly compared to previous years and contrary to seasonal trends."

The most "alarming trend" was a sharp rise in the number of roadside bombings, which soared 94 percent in the first four months of this year compared with the same period in 2009, Ban said.

Moreover, assassinations of Afghan government officials jumped 45 percent, mostly in the ethnic Pashtun south, he said. NATO has launched a major operation to secure the biggest southern city, Kandahar, the Taliban's spiritual birthplace.

At the same time, suicide attacks are occurring at the rate of about three per week, Ban said, half of them in the south. Complex attacks employing suicide bombers, rocket-propelled grenades and small arms fire were running about two a month, double the number in 2009, he added.