The Iraqi journalist who hurled his shoes at President George Bush was viciously beaten after being taken into custody, according to a police officer who accompanied him to prison.

Wrestled to the ground and then buried under a frantic mound of security officers, Muntazer al-Zaidi was last seen being dragged into detention. Controversy has since raged over what treatment was meted out to the man hailed a hero in many parts of the Arab and Muslim world for his protest against the invasion of Iraq. Yesterday there were further demonstrations in the Middle East calling for his immediate release.

Witnesses to his arrest and imprisonment have told the Observer Zaidi was badly beaten, during and after his arrest last Sunday, and that he risks losing the sight in one of his eyes as a result.

He is expected to be charged with insulting a foreign leader, which carries a prison sentence of up to two years. His family have received offers from hundreds of lawyers across the region willing to represent him.

An Iraqi judge appointed to investigate his treatment, and who has seen him in his prison cell, said Zaidi has bruises on his face and around his eyes. These, said the judge, had been sustained during his arrest at the Baghdad news conference during which Zaidi threw both his shoes at Bush, shouting: "This is the farewell kiss, you dog."

His family, who have been denied access to him, have claimed he suffered far more extensive injuries and was subjected to a prolonged and vicious beating, suffering a broken arm, broken ribs and internal bleeding. The allegations appear to be borne out by those who have seen him since his arrest.

One police officer, who accompanied him to prison, said the journalist, a Baghdad correspondent for the Cairo-based Al-Baghdadia TV, had been subjected to violence throughout the journey. The officer, who asked not to be named, said he witnessed security forces beating Zaidi in the car with such force that his ribs were broken. "I felt sorry when I saw them beating him. His mouth was badly injured and he did not utter a single word throughout until one of the guards hit him in his left eye with a gun. Then he cried out that he couldn't see, and I saw blood inside his eye. I am a police officer but even I have to say I felt proud of what he did."

A doctor called to examine Zaidi said his right arm had been broken and he had haematomas - indicative of internal bleeding - all over his body, particularly on his left leg, shoulders, face and head. The doctor, who also asked to remain anonymous, said specialists called in to treat him warned security guards that they must make sure his eye was protected for fear of a further haemorrhage which could cause him to lose his sight.

Zaidi's family allege that it is because of the severe nature of his injuries that he has not been called before a public court. As calls for his release were continuing, details of how he planned his extraordinary protest have begun to emerge.

Born into a traditional Shia family, Zaidi made no secret of the fact he was vehemently against the US-led occupation of Iraq and, according to family and friends, had said many times he would like revenge on Bush. A younger brother, Haythem, said Zaidi had unexpectedly found himself called on to cover the press conference held by Bush and Iraqi prime minister Nouri al-Maliki. His first action, it seems, was to return home immediately to change his foreign-made shoes into Iraqi-made ones.

A colleague at the TV station said Zaidi mentioned just before going home that "if something had to be done, it had to be 100 per cent Iraqi".

"Muntazer had repeated many times that if he had the chance, he would take revenge against the US president," said the colleague. "He held him responsible for the deterioration of the conditions we were living in. He just didn't have the chance before, and being asked to cover the conference was an opportunity for him. I am proud of him because he did what all of us have dreamed of doing, but were too scared to do."

Yet there is some confusion over whether the world's most famous shoes were indeed Iraqi. While another brother, Durgham, has insisted they were from the Baghdad factory of Iraqi shoemaker Alaa Haddad, cobblers from Turkey, Lebanon and even China - where most of Iraq's shoes are produced - have lodged rival claims.

Istanbul producer Ramazan Baydan insists the brown thick-soled shoes are his and currently known as Model 271 but soon to be renamed the Bush Shoe, or the Bye-Bye-Bush Shoe. He has hired an agency to promote them, claims to have taken 300,000 orders since the protest and plans to employ 100 extra staff to meet demand.

The originals, however, have been destroyed by investigators trying to determine whether they had contained explosives, which may come as a blow to Zaidi when he learns that Saudi Arabian Mohamed Makhafa had, reportedly, offered $10m for his 'shoes of dignity' and their 'high moral value'.

Friends of Zaidi speak of a dedicated journalist who lives in a small flat filled with books, many of them religious, and who was deeply interested in humanitarian issues. His political beliefs, however, remain unclear.

One colleague alleged he had been a Baathist under Saddam Hussein's rule and after the US-led invasion turned into a defender of religious cleric Muqtada al-Sadr's ideals. "I know people are seeing him as a hero, but he would do anything to become famous," said the colleague. "He said many times that he would like to become president of Iraq." Others, however, vehemently disagree with these claims.

Ahmed Ayssam, who graduated with him at the Communication College in Baghdad, described him as hard working and preferring to spend time with his books and family rather than going out. "He wanted to make a difference since he was a student, and he did it,' said Ayssam. "He is an example of faith and strength. He is a loyal friend, a hard worker, and if the Iraqi government allows it, a brilliant journalist without limits."

Zaidi, according to the prime minister's spokesman, has since written a letter begging for a pardon and regretting his "ugly act". His family are sceptical about this, believing it either to have been written under duress, or to be a straightforward fake. "I am suspicious ... because I know my brother," said Durgham.

The family believe his actions may have placed both them and himself in danger and claim to have received threatening calls. "There are thousands of supporters out there who applaud what he did, but there are also thousands that regret his actions and it has put his life in danger," said another brother.

"I am worried this has become dangerous for him, and about how long he will be alive for when he comes out of prison. It is a very delicate situation. I believe we will have to fight to stop him becoming a martyr."