US spokesman strongly denies abuses in Nerkh district, where locals say a string of civilians have vanished into military base

When relatives identified three mutilated bodies dug up near a former US special forces base as their missing family members, they decided to take the corpses to the capital of restive Wardak province and organise a protest to spread word of their loss.

By noon on Tuesday, hundreds of people had flooded the streets of Maidan Shar town, blocking the main road to Kandahar and Kabul and shouting "Death to America" and "Death to special forces". By early afternoon two more men were dead and one seriously injured after police opened fire to control what they said was an increasingly violent crowd.

The three bodies were just the latest grisly discovery in the troubled Nerkh district, where locals say a string of civilians disappeared into a military base housing US special forces. They claim they were then tortured and killed. Their families blame American forces, although the base was shared with Afghan troops and a US military spokesman strongly denied any abuses by foreign soldiers.

But locals have continued to blame US forces. "We have found 10 bodies of people killed by Americans in total, seven before and three more today, on the west side of the US base," said Sediqullah, a de-miner whose brother's body was one of the three found on Monday.

"His name was Atiqullah, he was 38 years old and a shopkeeper in Maidan Shar," said the 42-year-old, before going on to list the names and professions of the other dead, who included a teacher, a taxi driver, a government worker and casual labourers. He said their bodies bore signs of torture.

"They cut their fingers and beat their stomach and head with rocks," he said by phone from his home just outside Maidan Shar. "They were poor people who just had ordinary business and were just working to feed their families."

A senior Wardak politician said the 10 men all vanished at the end of last year, and their families had been seeking news of them for months.

"When there was a lot of snow, about 10 people disappeared in Nerkh and already about a month and a half ago seven bodies were found. The last part of the process was today, when three more bodies were found," said Hazrat Mohammad Janan, deputy head of the provincial council. "It is not clear who killed them, though protesters were accusing the US soldiers."

Wardak was at the heart of a showdown between the Afghan president, Hamid Karzai, and US forces earlier this year. Karzai ordered all foreign special forces troops out of the province after receiving reports claiming that the elite units had been involved in the disappearance of civilians in Nerkh.

Eventually the two sides agreed that while special forces would leave that district, they would stay on in the rest of Wardak, a province with a heavy Taliban presence, until Afghan forces were better prepared to battle the insurgency alone.

Meanwhile government investigators continued to pursue the claims and now believe that at least 17 people from the province disappeared into US custody, the New York Times reported recently.

Most have now been found dead, and authorities want to arrest a man they say was part of a special forces unit operating there, the paper said. Evidence includes a video of a torture session conducted by "Zakaria Kandahari", who investigators say is of Afghan descent but was raised in the US.

The US military says its forces played no role in deaths or torture in Nerkh. "We are absolutely confident, based on the investigations that we have done, that neither US or coalition forces were involved in any unlawful deaths in there," said a spokesman, Colonel Tom Collins.

However, Afghan investigators insist that at the very least, the US military must have been aware of abuses of detainees taking place at a compact and isolated base, the New York Times said, citing members of the investigating team.

Atullah Khogyani, spokesman for the provincial governor, said 500 people joined the protest, and the government has ordered a delegation to investigate the three men's disappearance and death, but declined to comment further.

The protesters said they did not need further proof. "They found them under some rocks, just thrown down on the ground," said 22-year-old Atiqullah, a taxi driver who had the same name as one of the dead men but did not know him.

• Mokhtar Amiri contributed reporting