Relatives of the man are seeking legal advice on whether they can secure the reopening of the investigation. They suspect the policemen detained him for seeking work in Um Touba, a Palestinian village inside Israel, without a permit, tied him to his own mule and drove it off at a gallop.

Police denied the family's version of events and said an investigation had been completed on 11 December and all border police in the area at the time had been "completely cleared" of acting in any way improperly.

The man, Mahmoud Shawawreh, 45, who had six children, left his home on his mule for the neighbouring village of Um Touba on the day of the incident. Relatives said he refused to join six other similarly detained men, including his brother Daoud, 50 in a journey by police van to a Jerusalem police station because he did not want to leave his mule behind.

Daoud Shawawreh said he left separately at about 7.30 am for the neighbouring village to begin work clearing a football field. He was stopped after admitting he did not have a permit. He said he and five other men had been told to get into a police van and were taken to the Talpiot police station. He was released at 11.30am and taken to the main Bethlehem checkpoint on the road from Jerusalem from where he took a taxi home.

He said that after being stopped by police and told to wait at the football field while they completed their tour of the village, he met his brother Mahmoud who had arrived with another man from his home in Um al Neu'uman. They had no permits either, and were told by police they would need to attend a police station.

Mr Shawawreh added: "One of the policemen in the van had Mahmoud's ID card and told Mahmoud to follow us with his mule to the police station. He said, 'I can't take it to that place. It's too far. A policeman who was with Mahmoud took the ID card from the guy in the van. When we left in the van I saw two border police Jeeps and two policemen with Mahmoud. There may have been more there, I don't know."

Mr Shawawreh said that at about 4pm a cousin, also called Mahmoud, told him his brother had been found unconscious and badly injured. "Mahmoud told me he had been with my other brother Jamal on the edge of Um Touba and had seen the mule and Jamal's son Mohammed, who was trying to hold it.

"Mahmoud recognised the mule and said to Mohammed where's your uncle. He pointed to the ground and said, 'There he is'. He was on the ground covered in blood and soil."

Mr Shawawreh said that after his brother's death in Jerusalem's Hadassah hospital five days later from his injuries, which included a fractured skull, a police investigator asked him whether he suspected that his brother had been killed. "I said, 'I don't know what happened to him. The last time I saw him he was with you. If you tied him to the mule I didn't see it'."

The incident came to light in a report in the daily Haaretz saying a man named Mohammed Hamdan saw the animal running and dragging something which looked from a distance like discarded metal. When the animal came closer he realised it was a wounded man. He stopped the animal and recognised Mahmoud Shawawreh, whom he knew well.

He told the newspaper he untied Mahmoud from the mule, and lay him on the ground, pushing his chest to help him breathe. He then called a local ambulance. Haaretz says its reporters spoke to another man in the Bethlehem area who who also claims to have been tied to a donkey in another incident.

Jamal Shawawreh said yesterday: "I saw [Mahmoud] on a dirt road in an area called Latun. I saw him covered with blood. The left side of his skull was smashed and part of the left side of his body as well.

He continued: I didn't recognise him at first. I don't know whether his injuries were from the pulling of the mule or whether he might have been beaten first."

Police said the first time border force was involved was after the man had been found and an ambulance called. Mickey Rosenfeld, the Israeli police spokes-man, said the injured man had been dragged by a donkey but added: "There was an internal investigation which cleared the border police of any involvement whatever in this individual's death."

He said that "once again" police had answered a summons for help and people had "taken advantage of them to try and get financial benefit or for whatever other reason".

The family refused to allow a post-mortem examination - as Palestinian families often do for religious reasons - but the Israeli human rights agency Btselem suggested the police should have insisted on one. The Israeli High Court ruled recently in a case involving a Jewish prisoner who died in mysterious circumstances that an autopsy should be held although his relatives had objected.