Concerns are rising that a high-profile attack may be planned by Taliban or Al Qaeda forces to disrupt Afghanistan's process of choosing a transitional government next month, officials said Tuesday.

U.S. and Afghan officials said they have no information about specific threats, but there have been recent reports about possible attacks on the Afghan capital, Kabul, where 1,051 representatives from across the country will meet June 10-15 to replace the transitional government installed by the United Nations in December.

In addition, the United Nations said Tuesday it was "deeply disturbed" at reports that participants in the loya jirga, or grand council, process are being intimidated, threatened and even detained in western Herat province.

Eight Afghans associated with the run-up to the meeting have been killed this month, one in Kabul, four in Kandahar and three in the central province of Ghor. U.N. officials emphasized they had no direct evidence linking the deaths with the selection process.

Mohammad Abil, spokesman for Defense Minister Mohammad Fahim, said he was aware of the reports of Taliban and Al Qaeda regrouping in northwestern Pakistan but said he knew of no specific threats toward Kabul as the loya jirga meeting approaches.

"All the time they are trying, they are plotting. There is no doubt about that. They are very active. But we don't know of anything in particular," Abil said.

The New York Times on Tuesday quoted Maj. Gen. Franklin L. Hagenbeck, commander of the American-led forces in Afghanistan, as saying U.S. intelligence suspected Al Qaeda and Taliban were planning to disrupt the loya jirga, possibly with suicide bombings.

"They are looking for something that will gain them a lot of publicity," he told the newspaper. "They are looking for something violent that would be, in their eyes and internationally, so spectacular that it would convince the local populace who are now sitting on the fence supporting us that they need to re-embrace the Taliban."

Hagenbeck also said that virtually the entire senior leadership of the Taliban and Al Qaeda have been driven out of Afghanistan and into the tribal border areas of Pakistan.

Citing intelligence reports, Hagenbeck said as many as 1,000 non-Afghan fighters may be with them in Pakistan's rugged and deeply conservative tribal belt that borders Afghanistan. They are hiding out there, he said, with Taliban allies.

Brig. Gen. John Rosa Jr. of the Joint Chiefs of Staff said Tuesday he had not seen any intelligence reports warning of specific plots targeting the loya jirga. He and Pentagon spokeswoman Victoria Clarke said they were sure some Taliban and Al Qaeda members were in Pakistan's tribal areas but had no way to guess where and how many there are.

"If we knew exactly where these people were, then we'd probably have them," Clarke said.

Two former high-ranking Taliban officials told The Associated Press last week that the Afghan-Pakistan border can't be sealed to stop the movement of militants. They said the Taliban's supreme leader, Mullah Mohammed Omar, is overseeing a reorganization of the religious movement and has been in contact with Taliban warriors in their mountain hide-outs in Afghanistan.

Involvement in the process of rebuilding Afghanistan's government has proven dangerous. In addition to the eight deaths of participants in the loya jirga process, Civil Aviation Minister Abdul Rahman was killed in February under mysterious circumstances aboard a plane at Kabul Airport. A bomb blast in April targeted Defense Minister Fahim as he arrived in the eastern city of Jalalabad. He was unhurt, but five people were killed and 52 injured.

U.N. spokesman Manoel de Almeida e Silva said two representatives selected in phase one of the loya jirga process were arrested in Herat in recent days. Another was detained, and he cited "a number of incidents of intimidation" in several districts of Herat.

If the commission decides fair and free local meetings — held to pick delegates — are impossible in an area, it is empowered to choose its own delegates who will then participate in the second phase — something Almeida said may soon happen in 20 western districts.

The United Nations has sent investigators to the Herat region and asked the provincial government and Afghanistan's interim administration to look into the problems, Almeida said. The Special Independent Commission for Convening of the Emergency Loya Jirga said it was also conducting an investigation.