An Afghan intelligence official has accused Pakistan's spy agency of planning the April assassination attempt on Afghan President Hamid Karzai.

Sayed Ansari, a spokesman for the national intelligence agency, told reporters today that Pakistan's Inter-Services Intelligence or ISI was involved in the attack on Mr. Karzai.

The Afghan president was unharmed in the April 27 attack on a military parade in Kabul, but three people were killed.

Ansari says phone calls linked to the attack can be traced back to Pakistan.

President Karzai's spokesman, Homayun Hamidzada said Tuesday a "foreign intelligence agency" was responsible for the assassination attempt, without naming a country or agency.

Afghanistan's intelligence chief, Amrullah Saleh, has said there is evidence that militants based in Pakistan's tribal region planned the attack.  

Relations between Afghanistan and Pakistan have been strained in recent weeks, since President Karzai threatened to send Afghan troops into Pakistan to fight Taliban militants.

In other news, the U.S.-led coalition in Afghanistan says its troops killed 22 militants after they attacked two towns in the east of the country Wednesday.

The coalition says it carried out airstrikes on Taliban insurgents after they attacked government offices in Sarobi and Gomal in Paktika province.

Earlier today, NATO-led forces in southern Afghanistan said an explosion killed one soldier in Nahri Sarraj district of Helmand province.  

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