United Nations Secretary General Ban Ki-moon has told member states of the international body about "grisly reports" of Syrian government forces arbitrarily executing, imprisoning and torturing people in the flash point city of Homs.

In some of his toughest criticism of Damascus to date, during Friday's address, Ban said "the Syrian government has failed to deliver on its responsibility to protect its people," and that "civilian losses have clearly been heavy. We continue to receive grisly reports of summary executions, arbitrary detentions and torture".

Ban went on to say "this atrocious assault is all the more appalling for having been waged by the government itself, systematically attacking its own people."

Taking to the podium after Ban, Syria's ambassador to the UN, Bashar Jaafari, told the 193-member General Assembly that Ban's statements were "slandering" his country.

Ban's remarks included "extremely virulent rhetoric that confines itself to slandering a government based on reports, opinions or hearsay" said Jaafari.

Speaking for 45 minutes, the Syrian envoy said the UN chief's statements "come from the opposition or from people who are abroad or people who are living in countries which are open enemies of Syria."

He added that reports of a humanitarian crisis were "absolutely false."

During his speech, Jaafari was extremely critical of the United Nations and other Arab states for their handling of the Syrian crisis.

"The secretary-general is not duly informed," he said, reiterating that the Syrian opposition consisted of "armed
terrorist groups."

Earlier on Friday, Ban made a plea for Damascus to grant access for aid workers to besieged Syrian towns, describing images of death coming out of them as atrocious.

Ban was speaking to reporters after the International Committee of the Red Cross told Syria it was unacceptable that its aid convoy had been prevented from entering a battle-scarred district of Homs where the opposition said President Bashar al-Assad's army had committed a massacre.

"It's totally unacceptable, intolerable," he said.

"How as a human being can you bear ... this situation? That really troubles me. I'm deeply sad seeing what's happening."

Source: Al Jazeera and agencies