A dramatic increase in the number of homemade bomb attacks is part of an "alarming trend" in Afghanistan, a UN report released Saturday said.

The report to the UN Security Council said bombings and assassinations have soared in the past four months amid ramped-up military operations in the Taliban-dominated south.

The number of attacks involving improvised explosive devices increased by 94 per cent over the same period in 2009, while assassinations of Afghan officials rose by 45 per cent.

"The rise in incidents involving improvised-explosive devices constitutes an alarming trend," the report said.

Suicide attacks occurred at a rate of about three a week, half in the restive south. Such bombings have tripled this year compared with 2009.

The increase in "complex attacks" — using a combination of suicide bombers and small-arms fire — pointed to Taliban groups linked with al-Qaeda, the report said.

The study found some encouraging signs, however, including the government's plan to reach out to insurgents and offer economic incentives to leave the battlefield. It also said the UN was working with Afghan officials to prepare for parliamentary elections in September.

NATO sees progress despite security concerns

Nevertheless, the UN found the number of security incidents had "increased significantly compared to previous years," in large part because of more military operations in the south early this year.

NATO spokesman Brig. Gen. Josef Blotz told reporters in the capital on Saturday that despite negative assessments, the international force was making steady strides.

"Tough fighting is expected to continue, but the situation is trending in our favour as more forces flow into the area," Blotz said.

He said joint NATO and Afghan forces were stepping up the pace of identifying and killing those responsible for attacks. Insurgent commanders were being apprehended by coalition forces, which over time will disrupt the ability to organize suicide and roadside bomb attacks, he said.

"It has to be tougher perhaps before it goes easier," Blotz said.

Blotz said the number of civilians killed or wounded in operations involving the international force dropped 44.4 per cent in the past 12 weeks, compared with the same period in 2009.

"In the same period of time, the number of civilian casualties caused by the insurgency increased by 36 per cent," Blotz said.

With files from The Associated Press