AMMAN -- Britain said Sunday it was deeply concerned by emerging reports of a "brutal massacre of civilians" in a Damascus suburb where activists claim more than 300 people have been killed over the past week in a major government offensive to take back control of rebel-held areas in and around the capital.

The British-based activist group Syrian Observatory for Human Rights said 32 more dead bodies were found in the streets of Daraya on Sunday and that they had been killed by "gunfire and summary executions." Among them were three women and two children, the group said. It put the toll for the past week at at least 320.

Another activist group, The Local Communication Committees, claimed 300 bodies were discovered Saturday in Daraya and 633 people have been killed there since the government launched its assault last week.

Britain's Middle East Minister Alistair Burt said if confirmed, the massacre "would be an atrocity on a new scale requiring unequivocal condemnation from the entire international community." He added that it "highlights the urgent need for international action to bring an end to the violence, end this culture of impunity and hold to account those responsible for these terrible acts."

Burt said he had discussed the killings with U.N. and Arab League Joint Special Representative for Syria Lakhdar Brahimi.

It is impossible to independently verify the death tolls for the town because of severe restrictions

on media coverage of the conflict. However, activists and residents have reported excessive use of force by the regime in major battles, with indiscriminate shelling from the ground and the air.

The LCC said some of those killed by regime forces in Daraya were buried in mass graves on Sunday. Video footage posted by the group showed bloodied bodies wrapped in colorful blankets lying next to each other with branches of date palms strewn over them.

Another video posted on the Internet and dated Saturday shows dozens of bodies on the floor of a mosque in Daraya. Most of the bodies are bloodied and wrapped in blankets. The anonymous commentator said there were at least 150 bodies there and blamed a pro-government militia known as shabiha for the killings. The authenticity of the two videos could not be independently confirmed.

On Thursday, troops backed by tanks and helicopter gunships stormed Daraya after intense shelling and fighting that lasted days.

The battle for Daraya showed the regime to be struggling to control Damascus and its suburbs though the firepower available to it is far superior than anything the rebels might have. Government forces are stretched thin, with a major ongoing battle for control of the nation's largest city, Aleppo in the north, as well as smaller scale operations in the east and south.

On Sunday, regime forces also used helicopter gunships and tanks to pound rebel-held areas in the northern city of Aleppo and the restive southern town of Daraa along the Jordanian border. The Observatory said it had reports of fatalities, but did not have exact numbers yet.

Activists say more than 20,000 people have died in 17 months of fighting in Syria, as an uprising that started with peaceful protests against Assad's rule has morphed into a civil war.

In Damascus, Syrian Vice President Farouk al-Sharaa appeared in public for the first time in several weeks for a meeting with a senior Iranian official, ending rumors that he had defected. Reporters saw him get out of his car and walk to his office for a meeting with Alaeddin Boroujerdi, head of Iran's powerful parliamentary committee on national security and foreign policy.

There have been a series of high-level defections from the Assad regime in the past few months.

Al-Sharaa was last seen at the funeral of four top security officials killed in a blast in Damascus on July 18. Since then, there had been rumors that he defected to Jordan, though al-Sharaa's office and Jordan repeatedly denied he defected. He was seen at the door of his office, shaking hands with Boroujerdi, according to an Associated Press reporter at the scene. He said al-Sharaa looked serious and steered away from reporters covering the meeting. He did not make a statement.

Pan-Arab satellite channel Al Arabiya reported that air force intelligence chief Maj. Gen. Jamil Hassan had been assassinated, but a senior government official denied it. The official insisted on anonymity because he was not allowed to speak to the media. The Al Arabiya report said Hassan, a powerful member of Assad's inner circle and religious Alawite minority, was shot dead Saturday by one of his aides who defected to the opposition.

Addounia TV, a pro-Syrian government channel, also denied the report. It said Hassan is "fine and the news about his killing is absolutely untrue."

In neighboring Jordan, officials say the country is bracing for a mass exodus of Syrians in the wake of intensified fighting.

Jordan appealed for increased international assistance to 160,000 Syrian refugees it is hosting. Information Minister Sameeh Maaytah said the refugee influx has swelled even further, with more than 2,300 Syrians crossing into Jordan on Friday -- the largest arrival in a single day since the outbreak of the Syrian uprising in March 2011.

"The number of refugees is growing and our limited resources are thinning," Maaytah said. "The international community should come to the aid of the Syrian refugees."

The United Nations refugee agency said it has yet to secure half of the $190 million aid appeal launched earlier this year to support Jordan and other countries hosting some 200,000 registered Syrian refugees.

Jordanian police spokesman Col. Mohammed Khatib said a Syrian rocket fell in the northern border town of Ramtha late Saturday, but no injuries were reported. It was the seventh rocket to fall in Jordan in five days, underlining the intensity of the army assault on southern Syrian towns such as Daraa, the birthplace of the uprising against Assad.

A police statement said 200 Syrian refugees pelted stones on Jordanian security guarding their desert camp late Saturday, wounding several policemen. The refugees were protesting poor conditions at the camp.

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Associated Press reporter Albert Aji in Damascus, Syria, contributed to this report.