As diplomatic efforts to end Syria's crackdown continue, an international rights group says Syrians detained during the uprising against President Bashar al-Assad have been subjected to torture.

Amnesty International says the treatment of detainees in Syria amounts to crimes against humanity. The group issued a report Wednesday based on interviews with 25 Syrians who said they endured torture at detention centers before they fled to neighboring Jordan.

The report comes as the United Nations-Arab League special envoy for Syria says Mr. Assad's government has responded to his overtures to end the crisis but questions remain.

A spokesman for envoy Kofi Annan said the former U.N. chief is seeking clarification on proposals Annan made in Damascus over the weekend. Syria responded on Tuesday.

The spokesman said “time is of the essence,” considering the “grave and tragic situation” in Syria.

U.N. officials estimate that 7,500 people have died in the year-long series of protests and government crackdown. The Syrian government blames the unrest on “terrorists” and outside agitators.

Amnesty researcher Neil Sammonds told VOA the report from his group documents 31 methods of torture used by security forces, army and pro-government armed gangs in Syria.

“Some of these forms of torture we see a kind of resurgence of methods and levels of abuse which we haven't really seen since the dark days of the 1980s when Bashar al-Assad's father, Hafez, of course was in power.”

He said the number of people who died under “highly suspicious circumstances” while in detention in Syria has been increasing, with 88 cases in the first five months of the uprising, and now a total of more than 270, a year after protests began.

“Definitely the human rights situation is worsening in the country, and we continue to call for the situation there to be referred to the prosecutor of the International Criminal Court because crimes against humanity are taking place.”

Sammonds also said the group has second-hand information about cases of abuse by the Syrian opposition, but that they are “very small” compared to the abuses of Mr. Assad's government.

Government forces were reportedly attacking the southern flashpoint city of Deraa Wednesday after forcing rebels out of Idlib in the north over the weekend.