The government has instructed the police to take a defensive stance
A British expatriate businessman living in Athens has told how a pre-bedtime stroll with his dog led to an introduction to Greek police violence.
By Malcolm Brabant
BBC News, Athens
The man, who is in his 30s, and has asked not to be identified, contacted the BBC after witnessing what he says was unjustified brutality and aggression in the popular bar district of Gazi in the early hours of Sunday morning.
The alleged clash happened not long after scores of masked youths attacked a police station in the nearby district of Exarchia, where 15-year-old Alexandros Grigoropoulos was shot dead a week ago by police.
The businessman said that while he was walking his dog and came across a "largely peaceful" demonstration passing the bars and coffee shops about 3km (two miles) from the Acropolis. He decided to tag along.
There was a "carnival atmosphere", he said, as the demonstrators chanted slogans and invited young Greeks to put down their drinks and join the group.
"As the group, numbering about 600, walked up Pireos Street, several bus loads of riot police arrived and began to deploy at the front and back of the demonstration and on side streets," he said.
Greeks have been staging a peaceful vigil at the site of the boy's death
"After the majority of the protesters had passed one of these side streets, a group of riot police charged and forced about 15 young men and women into a dark shop front on the corner of the street.
"As the protesters put their hands on their heads to signify that they were not intending to fight, the police began beating individuals with their batons, issuing threats of extreme violence. The women were handcuffed together and the men strip-searched.
"Additional police joined the group to stop passers-by witnessing what was going on. Four young men aged about 20 and clearly not connected to the demonstration walked past. They were ushered on.
"As they were walking away, a riot policeman ran up behind one of the men kicking him in the back making obscene comments about his size. As the man turned, the policeman began beating the young man with his baton, striking him on the head and the side of his face."
The BBC asked Greece's police headquarters to comment on the allegations, and after initially denying knowledge of the case, returned our call within 10 minutes with a statement vigorously denying the use of force.
A spokesman said: "The incident happened late last night. A group of people were moving in Pireos Street. They started causing a disturbance and trashing things close to the Ministry of Employment."
"Three teams of police, comprising 60 officers were deployed and made 51 arrests in the presence of television cameramen," he added.
The police spokesman insisted this version of events was correct.
"If anything like the events described by your witness had taken place, the media would not have missed the opportunity to film it, as this is exactly the sort of thing they are looking for. It would have been extremely difficult to have missed such an incident at that particular location," the spokesman added.
'We are going to kill you'
Following the police statement, the BBC interviewed the British businessman again.
"I did not see a camera person there. I cannot believe they arrested 50 people. The impression I had was that there was no major trouble until the police arrived. I saw them smash a couple of cash machines and closed circuit television cameras on the street and there was some stone throwing," he said.
"There were elements who wanted to cause trouble," he acknowledged. "But others on the demo were trying to stop it. And it was the peaceful ones who ended up being beaten."
The witness, who speaks Greek, said he overheard the police saying to their detainees: "We have you now. You are out of your universities now… We are going to kill you."
One of the demonstrators told the BBC the same story almost word for word.
"The person in front of me was hit with a baton, as was the person behind. I fainted and they didn't get me. I was in a total panic. Anyone who moved got hit. Anyone who talked got hit," she said.
"A policeman kept on marching in front of us and screaming verbal abuse. He was saying we are going to kill you. It was very scary," she added.
'Enemies of democracy'
Since the death of Alexis, about 400 people have been arrested and 70 people injured.
The government has instructed the police to take a defensive stance to ensure that there is no more bloodshed.
Prime Minister Costas Karamanlis told President Karolas Papoulias that the "enemies of democracy" could not expect any leniency.
Amnesty International has criticised the riot police for using excessive force
About 12 hours before Alexandros Grigoropoulos was killed, riot police are alleged to have baton charged several thousand economic migrants and would be refugees who were trying to obtain the necessary papers to claim political asylum.
During the panic, one young South Asian man plunged head first into a concrete lined canal and was critically injured.
He has been on a life support in intensive care for more than a week. On Monday, doctors are due to turn off the machine to see whether he can survive unaided.
Amnesty International has criticised the riot police for using excessive force during the course of the past week.
The police claim that they are amongst Greece's most poorly paid public servants and are often forced to take second jobs to make ends meet.