Sayed Abdul Ghafar, the provincial police chief, insisted that his men had opened fire into the air only and dismissed allegations that they had caused casualties.
Contradicting claims by the US, Abdul Ghafar said that the people killed in the nighttime assault in Shinwar district were not fighters or Taliban members, but members of the public.
He said: "The coalition conducted independent operations in Shinwar and martyred three people. They were civilians."
The protesters chanted slogans against foreign troops, George Bush, the US president, and Hamid Karzai, the Afghan president.
"The Americans killed three civilians," said Rizwan Khan, a demonstrator.
"They were my neighbours and I knew they were not Taliban."
Others at the protest said the dead were an elderly man shot in a mosque and two other men, employed as drivers, shot in their homes.
|Protesters drag a traffic sign in |
the Nangarhar protest [Reuters]
But the US-led coalition said it had killed only fighters who had attacked troops searching for a "foreign fighter network".
"During the operation, several fighters were killed when they attacked coalition forces. Nine militants suspected of foreign fighter [facilitators] were detained," a statement said.
It is often difficult to verify events in Afghanistan, where thousands of Afghan and international soldiers are working against several networks opposed to the US-backed government, some of which have al-Qaeda backing.
International troops are regularly accused of mistaking civilians for fighters and of being heavy-handed in their operations.
The soldiers say they work on verified information and have the right to self-protection.
Most Afghans are already unhappy with the ongoing presence of foreign troops in their country seven years after they came to drive out the Taliban-led government.