NATO insisted Thursday that the war against the Taliban in Afghanistan is being won, despite reports by other organisations of a sharp upsurge in insurgent attacks this year.

US General Joseph Dunford, head of the NATO-led International Security Assistance Force (ISAF), said there was "indisputable" progress towards the goal of a secure and stable nation.

A study by the Afghanistan NGO Safety Office found attacks by the Taliban and other insurgents rose 47 percent in January-March compared with the same period last year.

The United Nations has separately reported a rise of almost 30 percent in civilian casualties in the first quarter compared with the same period last year, with 475 civilians killed and 872 wounded.

Dunford in a statement gave no figures for attacks but said 80 percent of them were in areas where less than 20 percent of the population lives.

Equally importantly, he said, surveys showed that Afghans "will simply not tolerate the oppressive policies imposed by the former Taliban government".

The Taliban's 1996-2001 government was toppled by a US-led invasion. The militants have battled the current Western-backed government and US-led foreign troops ever since.

The 100,000-strong ISAF force will end its combat mission by the end of next year and Afghan forces will soon take nationwide responsibility for security despite lingering concerns about their competency and motivation.

The ISAF chief said insurgents would face a combined Afghan army and police force of more than 350,000. It was "steadily gaining in confidence, competence, and commitment", he said.

"While numerous challenges remain, there are some basic facts that highlight the improved security across the country," Dunford said.

He said almost eight million children are in school, 40 percent of whom are girls, compared with one million -- almost all boys -- under the Taliban.

In 2002 only nine percent of Afghans had access to basic health care while now 85 percent can reach medical facilities in an hour, he said, and life expectancy was steadily rising.

"Under the Taliban, there were only 10,000 fixed phone lines, and today there are over 17 million people using cellphones," Dunford said.

Women now hold more than 25 percent of the seats in parliament and have a small but growing presence in the army and police, he said.

Some analysts are less confident.

"ISAF appears to have a strategy of optimism. It tries to find statistics to bolster the case that it is winning the war," said Kate Clark of the independent Afghan Analysts Network (AAN).

For example the rise in cellphone use, she told AFP, is due to the spread of new technology, not the fall of the Taliban.

"The Taliban are shifting targeting from foreign forces to Afghan forces and civilians connected with the government," Clark said. "You have to ask if the tide is really turning: it may not feel like that on the ground."

Military analyst Gary Owen, in a blog posting on the AAN website, said attrition -- the loss of a soldier through desertion, death or injury -- was the most serious problem facing the Afghan army.

He said it lost 27 per cent of its fighting force to attrition from October 2011 to September 2012.

In February, US officials said ISAF incorrectly reported a seven percent decline last year in Taliban attacks, saying that the number of attacks for 2012 had been roughly the same as the previous year.