* Statement is rare direct accusation against Islamabad
* Pakistan rejects blame for attack that killed nine
* Attack prompts most foreign vote observers to leave
By Maria Golovnina
KABUL, March 24 (Reuters) - Afghanistan accused Pakistan's intelligence service on Monday of staging last week's attack on a hotel in Kabul in which nine people including foreigners were shot dead by militants.
Afghanistan usually speaks of unnamed foreign powers when it wants to hint at a suspected Pakistani role in an incident, but the statement by Afghanistan's NDS intelligence agency pointed its finger directly at Islamabad.
Pakistan's foreign ministry rejected any responsibility for the gunmen who managed to smuggle pistols past the Serena hotel's heavy security cordon last Thursday.
They then waited for a hotel restaurant to fill up for an Afghan New Year dinner before emerging to shoot diners. Three children between two and five were found with bullets in their heads and four of the nine dead were foreigners. The death toll included an Afghan journalist with the AFP news agency.
"NDS investigations and findings after the tragic incident reveal that Pakistani intelligence services were involved in planning this heinous attack," the Afghan statement said.
Pakistan's foreign ministry called it "disturbing" that Kabul was implicating Islamabad in the attack. "We reject the insinuation. The tendency to immediately blame Pakistan is unhelpful and should be discarded," it said.
Afghanistan has long had an uneasy relationship with its eastern neighbour, accusing it of harbouring Taliban militants and helping them stage attacks on Afghan soil.
Although the Serena has been attacked before, it is heavily fortified and considered safe enough to accommodate foreign observers during a presidential election next month.
Most foreign observers have now pulled out of Afghanistan in the wake of the attack. The April 5 vote is intended to mark the country's first democratic transfer of power but the absence of many foreign monitors could undermine its credibility.
NDS said that according to its investigation, attackers had placed small pistols in their shoes in a sophisticated type of operation never before seen in Afghanistan.
"NDS officials are investigating how terrorist armed with pistols entered the heavily secured hotel and is also investigating the possibility of providing weapons to the terrorists from inside the hotel," it said.
Both Afghanistan and the United States, which is withdrawing most of its troops from the country this year, have long criticised Pakistan for not doing enough to crack down on militants holed up in the mountains straddling the Afghan-Pakistani order.
Pakistan says it is doing everything in its power and has portrayed itself as a victim of the increasingly bloody Taliban insurgency. (Additional reporting by Katharine Houreld in Islamabad; Editing by Tom Heneghan)