Foreign militants with links to al-Qaeda - some believed to have experience in Iraq - are trying to encourage Afghan insurgents to adopt more Iraq-style tactics against US forces, well-placed sources in eastern Afghanistan have told the BBC.
There has been a rise in violence ahead of next month's polls
According to these sources, the wider use of suicide bombings and kidnappings are included in the tactics.
These outsiders, some of them Arabs, have been offering large bounties to Afghans in Kunar province to kill US soldiers, two sources said.
They have been showing videos of kidnappings in Iraq as part of recruitment efforts, they said.
Kunar is where US forces suffered their heaviest combat losses since overthrowing the Taleban in 2001 when a special forces team was ambushed in late June and a helicopter sent to rescue them was shot down.
There have been persistent US military operations there since, which American commanders say have made inroads on militant strength in the area.
However, this recruitment and training drive has continued, several sources said - all of whom spoke only on condition their position or location not be identified.
With parliamentary elections due next month, the fear is these militants are seeking to fuel a new offensive in the last couple of weeks before polling day on 18 September.
One source was present as videos were shown by Arab nationals to a gathering of potential recruits in a residential compound in Kunar's remote Korongal valley.
"They showed us footage of kidnap victims in Iraq being beheaded," he said.
US troops have been disrupting militants in Kunar
"We were also given advice on carrying out suicide bomb attacks and promised money for our families."
They were told they would be paid thousands of dollars for capturing or killing American soldiers.
Other sources - who all spoke on condition they not be identified - confirmed this account.
They spoke to the BBC, they said, because they wanted to alert people to al-Qaeda's activities in Kunar.
Asadullah Wafa, the Kunar governor, said he could not comment on the accounts of these sources.
But he confirmed continued reports of foreigners infiltrating his province from across the border in Pakistan - among them Chechens and Pakistanis as well as Arabs.
Al-Qaeda's penetration of the area around the Korongal valley has been facilitated by a local Taleban commander called Ahmad Shah, who is also known as Ismail.
He narrowly escaped a US air strike in July after being tipped off.
'Time will tell'
It is not clear whether Ahmed Shah was in the area during the most recent US offensive in Korongal. But it was his supporters and his al-Qaeda backers who were the target.
Militants released a video of actions against US troops in Kunar
The US military says at least 40 suspected militants were killed in that operation.
But spokesman Lt Col Jerry O'Hara said this figure was an estimate and said he did not have details of their identities.
It is not clear either to what extent this operation has disrupted militant activities there.
"We achieved some success," Col O'Hara said from his office at the Bagram airbase. "But time will tell if this means an end to enemy influence there."
The spokesman said he had not heard of footage from Iraq being shown to potential recruits and that he had "no reports of videos being found".
But he said reports from Kunar and other areas suggested militant leaders were increasingly having recruitment problems and were having to resort to paying ever greater sums of money to persuade people to mount attacks.
"We've seen a 40% to 50% rise in the level of payments going to fighters," Col O'Hara said.
The threat of more extreme, Iraq-style tactics is being treated seriously in many quarters here as the elections approach.
Most recently, the Afghanistan Non-Governmental Organisation Security Office (ANSO) highlighted the issue in one of its regular briefings, focusing particularly on the east of the country.
"This warning should still be considered current," the agency said.