As the Syrian government's crackdown continues, a report says 88 protesters have died in custody since April. Human rights groups tell Channel 4 News there is evidence of "horrific cases of torture".
Violence in Syria is continuing, as forces loyal to President Bashar al-Assad try to suppress protests against the regime.
Residents say troops raided homes in Hama early on Tuesday as tanks rolled into the city. Syrian security forces have also reportedly shot at protesters during demonstrations in Deraa province, the suburbs of Damascus and the city of Homs.
Activists say four protesters, including a 13-year-old boy, were shot dead on Tuesday after Eid prayers in al-Hara and Inkhil in Deraa province.
'Tortured and mutilated'
The continued crackdown comes as Amnesty International claims 88 people held in Syrian custody have died in the past five months.
All of those killed were men or boys, including 10 children.
Amnesty spokesman Neil Durkin told Channel 4 News that at least 52 of those deaths were caused by "horrific" cases of torture carried out by forces loyal to Bashar al-Assad.
It's fairly common that people have had their genitals or other parts of their body mutilated. Some have had their eyes gouged. Neil Durkin, Amnesty International
"We've seen it's fairly common that people have had their genitals or other parts of their body mutilated.
"Some have had their eyes gouged. Others have been shot during protests and then taken into custody without their wounds being treated," Mr Durkin said.
Figures 'significantly higher'
Amnesty says it has the names of 1,800 people who have died in the crackdown so far, but spokesman Neil Durkin conceded the real figures could be much higher.
"It's a conservative but solid figure. We're quite careful about documenting evidence and cataloguing our information. But the nature of deaths in custody means it is likely to be significantly higher as it won't be at all publicised by the government."
President of the Syrian Human Rights Committee, Walid Saffour, told Channel 4 News that human rights groups were playing down the number of deaths to seem more legitimate.
More soldiers are refusing to follow the regime's orders and kill their own people. Their loyalty is to the people, not to Assad. But if they disobey orders they're shot at once. Walid Saffour, President of the Syrian Human Rights Committee
"The real number of people killed in custody is actually much higher. They're minimising the numbers to gain credibility."
Mr Saffour, who was himself detained and tortured during the government's bloody crackdown in 1982, said security forces today are using "more sophisticated methods" of abuse.
"The instant they are arrested they're subjected to beating. In jails they're using wire cables, knives, beating them with metal chairs. They're torturing them for hours or until they lose consciousness.
'Communications cut off'
Mr Saffour said he could not reach family members on Wednesday, as the internet and mobile phone connections continued to be disrupted.
"I tried to contact my son, my brother and my sister, but the phones are dead or have an engaged signal. But I am getting information through activists on the ground," he said.
The latest violence comes days after Syrian authorities said the army had withdrawn from Hama. The government has also denied persistent reports of a mass grave being uncovered in the southern city of Deraa.
Local activists reported gunfire in several cities across Syria early on Wednesday as the violence continued, but Mr Saffour said the number of soldiers defecting was on the rise.
"More soldiers are refusing to follow the regime's orders and kill their own people.
"Their loyalty is to the people, not to Assad. But if they disobey orders they're shot at once. And the government claims them as martyrs for the regime," he said.
Stronger stance needed
Amnesty has repeated its calls for the UN to take a stronger stance on the bloodshed.
Spokesman Neil Durkin told Channel 4 News that world leaders had to do more than simply slap sanctions on Assad.
"We want much greater action from the UN Security Council to impose an arms embargo which doesn't yet exist. And we want a referral to the International Criminal Court for these crimes against humanity," he said.