By Louis Charbonneau and Michelle Nichols
UNITED NATIONS (Reuters) - U.N. Secretary-General Ban Ki-moon turned up the pressure on Syria on Friday, telling U.N. member states of "grisly reports" of Syrian government forces arbitrarily executing, imprisoning and torturing people in the battle-scarred city of Homs.
"The Syrian government has failed to deliver on its responsibility to protect its people," Ban told the 193-nation U.N. General Assembly. "Civilian populations are under military assault in several cities."
"A major assault on Homs took place yesterday," he said. "Civilian losses have clearly been heavy. We continue to receive grisly reports of summary executions, arbitrary detentions and torture."
In some of his toughest criticism of Damascus to date, Ban added that "this atrocious assault is all the more appalling for having been waged by the government itself, systematically attacking its own people."
Syria's U.N. ambassador, Bashar Ja'afari, took to the podium to tell the assembly that Ban's remarks included "extremely virulent rhetoric that confines itself to slandering a government based on reports, opinions or hearsay."
Ja'afari said the false allegations "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."
"The secretary-general is not duly informed," he said, reiterating that the Syrian opposition consisted of "armed terrorist groups."
Earlier on Friday, Ban made an impassioned 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."
'RACE AGAINST TIME'
Earlier this month, the General Assembly overwhelmingly approved a non-binding resolution condemning Syria's crackdown and endorsing an Arab League plan for Assad to step aside.
In a rare show of unity with Western powers, Russia and China joined other U.N. Security Council members on Thursday in rebuking Syria for not allowing the U.N. humanitarian aid chief, Valerie Amos, into the country.
Russia and China twice vetoed council resolutions that would have condemned Damascus and demanded it halt the crackdown on anti-Assad demonstrators, saying Western and Arab nations were pushing for Libya-style "regime change" in Syria.
The United States is drafting a legally binding council resolution that would call for aid workers to be allowed into besieged towns and an end to the violence, U.N. envoys said.
Speaking on behalf of Saudi Arabia and the other Gulf Cooperation Council states, Saudi Ambassador Abdallah Y. al-Mouallimi told the General Assembly that Damascus had taken the Russian and Chinese vetoes as a "green light to roll over unarmed civilians in Syria and snuff out their revolution."
"It is a regime that behaves as if it were in a race against time to finish the job before the Security Council moves again," he said. "So we have witnessed a continuing escalation in attacks against civilians."
Ja'afari responded angrily to the Saudi speech, which he said contained many "dangerous things." He chided the Saudi envoy for using the term "regime" about Syria's government.
The United Nations says Syrian security forces have killed more than 7,500 civilians during an 11-month government crackdown on pro-democracy protesters.
Ja'afari repeated Syrian allegations that the opposition was being armed and supported by foreign countries and was using civilians as "human shields." He also denied that Damascus had refused to allow Amos into the country, saying his government was "ready to receive Ms. Amos."
(Editing by Peter Cooney)