The Afghan government blamed foreign spy agencies for a rising number of killings where government soldiers and policemen have gunned down their international partners, and ordered stricter vetting of recruits and screening of those in the 350,000-member Afghan security force.

The United States had no information suggesting that the insider attacks were the work of foreign intelligence services, a senior U.S. defense official said. Instead, he said attacks typically are carried out by Afghans acting on their own, although some might have had help, on occasion, from insurgent networks. The official spoke on condition of anonymity to discuss intelligence information about the attacks.

Afghan President Hamid Karzai summoned members of his national security council to the palace for an unscheduled meeting to discuss cases where members of the Afghan security forces or militants wearing their uniforms have turned their weapons on foreign troops. So far this year, there have been 32 insider attacks against coalition forces, resulting in 40 deaths, according to the NATO military alliance. That's up from 21 attacks for all of 2011, with 35 killed.

"The reports presented by the security officials in this meeting blamed the infiltration by foreign spy agencies into Afghan security force ranks as responsible for the rise in the individual shootings," Karzai's spokesman Aimal Faizi said.

He said the foreign agencies were trying to undermine confidence in the Afghan security forces.

"The investigation done so far shows there's definite infiltration by foreign spy agencies," Faizi told a small group of international journalists he invited to the palace to discuss the national security council meeting.

Asked if the foreign spy agencies suspected included those from neighboring countries, Faizi said, "Neighboring countries included, but I don't want to name any country."

In the past, intelligence agencies in neighboring Iran and Pakistan have been accused of enabling Afghan insurgents to destabilize the country.

A senior Pakistani intelligence official denied the country's involvement in the killings. He spoke on condition of anonymity in line with the agency's policy.

Iran also has denied allegations that it supports the Taliban.

The U.S.-led coalition has said only about 10 percent of the attacks were related to infiltration by the Taliban insurgency, but that analysis was done before the latest furious spate of seven attacks in 11 days.

Faizi said an Afghan investigation into the killings revealed a strong foreign connection. "That brings us to this conclusion that the foreign spy agencies are involved," he said.

He cited physical evidence collected from gunmen who were interrogated after some of the shootings, adding that the spy agencies apparently were using Taliban fighters or sympathizers as infiltrators.

"There are letters. There are papers that are authorizing them to do different things. There are telephone calls," Faizi said, without disclosing details of the investigation's findings.

Faizi said the foreign spy agencies were instigating insider attacks to undermine confidence in the Afghan forces, but he didn't elaborate about why they would want to do that other than to say that they feared a strong Afghan security force.

On Monday, President Barack Obama expressed deep concern about the insider attacks and discussed the problem Monday with the chairman of the Joint Chiefs of Staff, Army Gen. Martin Dempsey, who was already in Kabul to talk to American and Afghan officials about how to halt the killings.

Dempsey has acknowledged that efforts launched a year ago to improve the vetting of Afghan recruits have yet to solve the problem.

Earlier this year, the U.S. commanders assigned some troops to be so-called "guardian angels" -- watching over their comrades in interactions with Afghan forces and even as they sleep.

The U.S. also started allowing Americans to carry weapons in several Afghan ministries and started evaluating such visits to Afghan government offices with a stricter eye to security. And earlier this month, U.S. officials ordered American troops to carry loaded weapons at all times in Afghanistan, even when they are on their bases as a precaution against such insider attacks.

Faizi said Karzai's national security team decided at the meeting to further tighten the recruitment and vetting process and strengthen intelligence units within the defense and interior ministries.

The team also decided to investigate the cause of every insider attack and develop cultural training for police and soldiers to prevent personal disagreements between Afghan and NATO forces that have led to some of the shootings. The national security team also said a more comprehensive questionnaire would be introduced to screen recruits and officials will do more to check on members of the security forces with ties to Pakistan or Iran.

"They will study every single case of every individual who is either in the army or the police who has family either in Iran or Pakistan," Faizi said.

This is not a new procedure but one that should command greater attention, he said.

"There are some individuals within the Afghan security forces who still have families either in Pakistan or Iran, so there is still a connection between them and their families in those countries," he said.