DAMASCUS (AFP) ― Scores of civilians from President Bashar al-Assad’s minority sect were reported killed Tuesday as Washington blacklisted an al-Qaida-linked rebel group it accuses of hijacking the uprising in Syria.

More than 125 people were killed or injured by gunfire and several explosions that hit a neighborhood in central Syria mainly inhabited by Alawites, the Observatory said.

The area where violence broke out lies in a majority Sunni area, it added.

The Britain-based watchdog had earlier reported all 125 were civilians and that they had been killed or hurt by a string of bomb attacks. Observatory director Rami Abdel Rahman later clarified that an unknown number of the victims were in fact fighters.

“Between 125 and 150 people were killed or hurt by gunshots and explosions in the village of Aqrab,” Abdel Rahman said.

Aqrab is home to a majority of Sunni Muslims, but the neighborhood where Tuesday’s violence broke out is majority Alawite, Abdel Rahman and activists said.

“The Syrian Observatory for Human Rights received a series of contradictory reports on events in the village of Aqrab, which is inhabited by a minority of Alawites,” the Observatory said in an email.

“The Observatory calls on the United Nations to establish an independent inquiry of Syrian, Arab and international jurists whose transparency is proven, to investigate events in Aqrab as well as other massacres in Syrian towns and cities,” the watchdog added.

Reports of the mass killings broke hours after the United States blacklisted Al-Nusra Front as a “terrorist organization,” balancing its move with the announcement of fresh sanctions against pro-Assad militias.

The U.S. State Department said that despite its efforts to portray itself as part of the legitimate Syrian opposition, Al-Nusra was a front for the al-Qaida in Iraq organization.

“It is, in fact, an attempt by AQI to hijack the struggles of the Syrian people for its own malign purposes,” it said.

The Al-Nusra Front’s fighters, many of them jihadist volunteers from around the Islamic world, were instrumental in the fall of the army’s Sheikh Suleiman base in northern Syria on Monday after a months-long siege.

Its role in the seizure of the garrison, the government’s last between second city Aleppo and the Turkish border, undercut the military influence of the mainstream rebel Free Syrian Army.

An AFP journalist who witnessed the clashes around Sheikh Suleiman said many fighters were from other Arab countries and Central Asia.

The U.S. Treasury Department designated two of the Al-Nusra Front’s senior leaders, Maysar Ali Musa Abdallah al-Juburi and Anas Hasan Khattab, for sanctions.

It also imposed sanctions on two armed militias supporting the Assad regime as well as two shabiha (pro-regime militia) commanders.

At the same time, however, Washington said it had reason to ease the urgent concerns it had expressed in recent weeks about the dangers of Damascus resorting to use of its chemical weapons stockpiles against the rebels.

U.S. Defense Secretary Leon Panetta said Syria had not taken any new steps in recent days that signal a readiness to use its arsenal.

“At this point the intelligence has really kind of leveled off. We haven’t seen anything new indicating any aggressive steps to move forward in that way,”

Panetta told reporters aboard his plane before landing in Kuwait.

International military chiefs have met in London to discuss the Syria conflict, a diplomatic source said after a media report that they discussed plans to train rebels and give air and naval support.

A British diplomatic source confirmed that the military leaders had held talks, but played down the idea that they discussed military intervention against the Assad regime.

“As far as I know they didn’t explore options in any detail, certainly they didn’t explore options for military intervention,” the diplomat said on condition of anonymity.

Inside Syria, at least 68 people were killed in violence across the country on Tuesday, the Observatory said, noting that its preliminary toll excluded the victims in Aqraba pending further reports.

With the total death toll now topping 42,000, according to the Observatory’s figures, the U.N. High Commissioner for Refugees said the number of Syrian refugees in neighboring countries and the wider Arab world had now passed half a million.

“And these numbers are currently climbing by more than 3,000 a day,” UNHCR spokeswoman Melissa Fleming told reporters in Geneva.