The Afghan government says a "foreign intelligence agency" was responsible for an April assassination attempt on President Hamid Karzai.

Afghan presidential spokesman Humayum Hamidzada said Tuesday the investigation into the attack is continuing.  He did not name a specific country or agency.

He also said Pakistan must stop militants from crossing the border to attack targets in Afghanistan, otherwise Kabul would "take action to defend the country and people."

Mr. Karzai survived the attack at a military parade in Kabul with no injuries.  Three people died in the attack.

Afghanistan's intelligence chief Amrullah Saleh has said there is evidence that militants based in Pakistan's tribal region planned the attack.  But he said he had no proof the Pakistani government was involved.

Meanwhile, Afghan officials say a U.S.-led coalition airstrike has killed 15 militants who attacked a government building in eastern Afghanistan.

NATO forces bombed the militants Tuesday as they were withdrawing from an attack at government headquarters in Paktia province.  Officials say most of the militants killed were foreigners.

NATO officials also said a mine blast Tuesday killed one soldier and wounded three others in Khogyani district of Nangarhar province.

The incident comes a day after a suicide car bomber targeted a NATO-led convoy in western Herat province, killing five civilians.  Nineteen others were wounded in the attack.

Also in Herat Monday, local officials say unknown gunmen killed a woman police officer.  Officials say they believe she is the first woman police officer to be killed in the country.

Separately Monday, the U.S. military said coalition forces killed 55 militants, including three Taliban leaders, in Paktika province.

Some information for this report was provided by AFP and Reuters.