Syrian troops take position in a heavily dama
Syrian troops take position in a heavily dama AFP photo

There is a "high probability" that Syria used chemical weapons in the ongoing civil war, but final verification is needed, the chairman of the U.S. House Intelligence Committee told CNN on Tuesday.

"I have a high probability to believe that chemical weapons were used," Chairman Mike Rogers (R-Michigan) said.

"We need that final verification, but given everything we know over the last year and a half, I would come to the conclusion that they are either positioned for use, and ready to do that, or in fact have been used," he told CNN.

Rogers and Sen. Dianne Feinstein (D-California), chairwoman of the Senate Intelligence Committee, struck ominous tones in an interview on the news channel about the possibility that Syria had crossed what President Barack Obama has said was a “red line” that could lead to the United States getting involved militarily in the conflict.

Rogers' statement comes as the specter of chemical weapons attacks in the Syrian civil war emerged Tuesday, with the government and rebels each blaming the other for using such munitions.

State media reported that "terrorists fired rockets containing chemical materials on Khan al-Assal in Aleppo province," and Information Minister Omran al-Zohbi called the attack a "dangerous escalation," according to AFP.

Deputy Foreign Minister Faisal Muqdad said 31 people had been killed, and state media added that around 100 more were injured.

The rebels, however, denied the charges and accused regime forces of a deadly long-range missile attack that caused "breathing problems."

The Russian foreign ministry said it had "information" from Damascus that insurgents used chemical weapons, and expressed concern such weapons falling into the hands of rebels "complicates further the situation in Syria."

Responding to claims by the Syrian government and its ally Russia, White House spokesman Jay Carney said Washington has "no evidence to substantiate the charge that the opposition has used chemical weapons."

State Department spokeswoman Victoria Nuland said U.S. ambassador to Moscow, Michael McFaul, would also be seeking clarification from Russian authorities.

An Israeli source was more firm on the matter, confirming that chemical weapons were used in attacks on the cities of Aleppo and Damascus.

Syrian rebels say that Syrian President Bashar Al-Assad’s regime has already sent chemical weapons to Hizbullah. An Israeli expert made similar claims in March, and warned that Syrian rebels pose a greater threat.

Syria's chemical weapons stockpile, which dates back to the 1970s, is the biggest in the Middle East, but its precise scope remains unclear, according to analysts.

U.S. officials said a few months ago there was evidence that Assad's troops had not only moved deadly sarin gas that might be used against rebels, but also that its binary components, usually stored separately, had been combined and placed into bombs for use.

Obama has publicly warned Assad that the use of chemical weapons “would be totally unacceptable.”

"If you make the tragic mistake of using these weapons, there will be consequences and you will be held accountable," said Obama.