Taliban fighters 'killed' in battle

Speaking to the BBC in Afghanistan, Jaap de Hoop Scheffer said it was a major problem that had to be addressed.

In recent months, Nato officials have blamed the border areas for a steep rise in attacks inside Afghanistan.

Mr de Hoop Scheffer said the fighters gathering in Pakistan were an issue not only for the region but the world.

'Common effort'

The secretary general, speaking during an official trip to Afghanistan, said that finger-pointing and blaming Pakistan over the issue was not the way to resolve the problem.

"This is a major problem," he said. "The solution must be found in a common effort.

"I'm under no illusion that only Pakistan, or only the West, or only Afghanistan, can find the solution for the huge problem that has arisen there."

Mr de Hoop Scheffer was not specific about what kind of international effort he was talking about.

The US and Nato have a growing military presence in Afghanistan.

In recent months the US and its allies have pledged hundreds of millions of dollars in military and other forms of assistance to help Pakistan's new government tackle militancy in tribal areas along the border.

On a separate issue, the Nato chief expressed regret over civilian casualties at the hands of foreign forces after a string of incidents in which ordinary Afghans have died.

Earlier this month, an American air strike killed at least 50 civilians - most of them women and children - who were travelling to a wedding.

But, Mr de Hoop Scheffer added, there could be no "moral equivalence" between Nato forces and the Taleban on the issue of civilian casualties.