Afghan security forces surrounded a house in the capital Kabul on Wednesday and traded gunfire with Taliban insurgents before blowing up the building and killing two militants as well as a woman and child inside, officials said.
Earlier, an Interior Ministry official had said five Taliban militants blew themselves up in the house.
The two dead Taliban fighters were involved in a botched attempt to assassinate President Hamid Karzai on Sunday, but they had also received help from some government officials, senior ministers and a security official told a news conference.
"Investigations make clear that the enemy had infiltrated to some extent into some of our security organs and those involved have been arrested with all their networks," said Defence Minister Abdul Rahim Wardak.
The identities of those who helped facilitate the attack would be revealed after the president's approval, said the head of the National Directorate of Security (NDS), Amrullah Saleh.
Taliban gunmen fired rocket-propelled grenades and small arms at a state parade on Sunday sending President Hamid Karzai, his cabinet and the military top brass diving for cover. Three people were shot dead the before troops killed three Taliban attackers.
Members of parliament as well as the Afghan public at large have questioned how the Afghan police and NDS could have allowed such a breach of security at such a high-profile event.
While the Taliban have carried out sporadic suicide bombings in Kabul before, Sunday's attack, together with a guerrilla-style assault on a five-star hotel in the capital in January, indicate a more sophisticated mode of attack, designed to grab headlines.
The same Taliban network was behind both attacks, Interior Minister Zarar Ahmad Moqbel said.
Afghan security forces surrounded the house on a hillside close to the old city during the night following tip-offs from those arrested after Sunday's violence, Wardak said. After about 10 hours of battling the militants, NDS officers blew up the house killing the two Taliban fighters and a woman and child inside, Saleh said.
The Taliban have vowed to target Kabul this year as part of their campaign to overthrow Karzai's government and drive out the more than 50,000 foreign troops stationed in the country.
Afghan and international troops have steadily clawed back almost all of the towns in the south and east, but Taliban rebels are still active in much of the countryside. US Marines captured a town centre from Taliban insurgents in the southern Afghan province of Helmand on Wednesday, their first large operation in Afghanistan since arriving to reinforce NATO troops last month.
Washington sent the 3,200 Marines to southern Afghanistan to bolster British, Canadian and Dutch forces engaged in daily battles with Taliban militants there after other NATO allies failed to come up with large numbers of extra combat troops.
Taliban fighters fled Kabul in late 2001 to escape a US-led aerial onslaught and a ground assault by Afghan militia. In the years immediately after 2001, the Taliban regrouped and two years ago relaunched their insurgency with guerrilla attacks on Afghan and international troops mainly in the south and east, backed by suicide bombs across the country.