AAZAZ (AFP/Reuters) - UN investigators said Wednesday the Syrian regime had committed crimes against humanity, as at least 30 people were reported killed in a major air strike in a rebel bastion in the north.Regime forces were also bombarding the key battleground city of Aleppo in the north, activists said, while Damascus was shaken by a bomb attack targeting military headquarters and a firefight near the prime minister’s office.A report by the UN Commission of Inquiry said government forces and their militia allies committed crimes against humanity including murder and torture while rebel fighters were guilty of lesser offences.The report was issued as pressure mounted on President Bashar al-Assad’s embattled regime with the world’s largest Muslim body set to suspend Syria over the unrelenting violence, following a similar move by the Arab League.The UN investigators also said there were “reasonable grounds” to believe that government forces and their shabiha allies were responsible for other “gross violations of international human rights law” including arbitrary arrest, unlawful killing and indiscriminate attacks against civilians.Rebels were also responsible for abuses, the report said, although these “did not reach the gravity, frequency and scale of those committed by government forces and the shabiha”.The report was issued as reports emerged of a major air strike in Aazaz, a rebel bastion north of the second city Aleppo that activists said had killed at least 20 people, including children.“This was a civilian area. All these houses were packed with women and children sleeping during the fast,” said witness Abu Omar, a civil engineer in his 50s.“Only dogs can do something like this. Israel wouldn’t do such a thing in a war,” he told AFP.The Syrian Observatory for Human Rights said more than 20 people were killed, including civilians and rebels, in an attack on a Free Syria Army base, as Muslims were observing the dawn-to-dusk Ramazan fast.In all at least 63 people were killed on Wednesday in Syria, where more than 23,000 people have died in violence since an uprising against the regime erupted in March 2011, said the Observatory.In Damascus, the FSA claimed a bomb attack targeting a military headquarters near a hotel used by UN observers, saying it was a warning to Assad that it could strike anytime at the very heart of the regime.A gunbattle also erupted between rebels and troops near the offices of new Prime Minister Wael al-Halqi. Damascus has been rocked by several bomb blasts since the start of the increasingly brutal conflict, including a July attack also claimed by the FSA that killed four top security chiefs in a major body blow to the regime.Russia, meanwhile, said it would not let the West “sabotage” a political transition accord for Syria agreed in Geneva in June and accused Western states of fomenting violence by openly supporting the armed rebellion. World powers had agreed on a Russian-backed transition plan that did not make an explicit call for Assad to quit, although the West insists it sees no future role for the man who has led Syria with an iron fist for 12 years. “What was accomplished in Geneva should not be sabotaged,” Foreign Minister Sergei Lavrov told reporters in Belarus. “There is a need for outside players to put pressure on all Syrian sides, stop urging and inciting the opposition to continue the armed struggle,”A Russian official also said Moscow wanted to keep the UN monitoring mission operating in some form after its mandate expires on August 19, warning that a withdrawal would have “serious negative consequences”.China, which along with Russia has blocked three UN resolutions on Syria, also accused Western powers of hampering efforts to end the conflict, as a senior Damascus envoy visited Beijing for talks.“Some Western countries have never given up the goal of ‘regime change’ in Syria and constantly reinforced their support for the anti-government forces,” the People’s Daily in China said.US Defence Secretary Leon Panetta on Tuesday accused Iran’s elite Revolutionary Guards of trying to develop a militia within Syria to fight for the regime.A large Lebanese clan said it has kidnapped at least 20 Syrians to try to secure the release of a family member abducted near Damascus this week. “They were kidnapped because a member of our family was taken the day before yesterday in Syria,” family member Abu Ali al-Muqdad told AFP by telephone, adding that one of the Syrians was injured.Amid international concerns about the deteriorating humanitarian situation, UN humanitarian chief Valerie Amos was holding a second day of talks in Damascus on how to step up relief aid.