The Vatican's envoy to Syria Mario Zenari blamed both sides for violations in the conflict raging in Syria and called for humanitarian law to be respected in an interview aired on Wednesday.

"We have to demand that all sides in the conflict rigorously respect international humanitarian law which as we can see has fallen apart due to the fault of both warring sides," Zenari told Vatican radio.

Israeli Foreign Minister Avigdor Lieberman has called on the Middle East peacemaking Quartet to force elections on Palestinians in a bid to oust president Mahmoud Abbas and revitalize the dormant peace process.

In a letter sent on Tuesday to the Quartet's top diplomats, a copy of which was obtained by Agence France Presse, Lieberman said that Abbas "apparently is uninterested or unable... to reach an agreement which would bring an end to the conflict."

France is providing the Syrian opposition with "non-lethal" military aid, Prime Minister Jean-Marc Ayrault said Wednesday.

Speaking on BFMTV-RMC radio, Ayrault said France had responded positively to a request for help from the rebels seeking to overthrow Syrian President Bashar Assad.

The longest serving Syrian prisoner in Israel has been freed after 27 years behind bars, Syria's official news agency SANA said on Wednesday.

It said Sedki al-Maket, who was arrested in August 1985 for resisting the Israeli occupation of the Golan Heights, was released and had returned to his home town on the strategic plateau.

Syrian military planes pounded a rebel-held area of the northern city of Aleppo on Wednesday as opposition fighters claimed to have seized parts of a town on the Iraqi border, a watchdog said.

Twelve people were also killed by troops in a raid on a Damascus district, according to the Syrian Observatory for Human Rights, a day after it reported dozens killed when regime forces stormed another suburb of the capital.

The United States expressed deep skepticism Tuesday about suggestions by Syria's deputy prime minister that the regime was open to discussing Syrian President Bashar Assad's resignation.

"We saw the reports of the press conference that the deputy prime minister gave. Frankly, we didn't see anything terribly new there," State Department spokeswoman Victoria Nuland said.

Israeli Prime Minister Benjamin Netanyahu on Tuesday strongly condemned a brutal hate attack on young Palestinians last week in Jerusalem, describing it as a combination of "racism and violence."

"In the state of Israel we will not tolerate racism nor the combination of racism and violence," he said in remarks relayed by his office.

The Syrian National Council, Syria's main opposition group is studying the formation of a transitional government, its leader Abdel Basset Sayda said Tuesday.

"We are currently studying the formation of a transitional government," Sayda said after meeting French President Francois Hollande in Paris against a background of hints from the Syrian regime that President Bashar Assad could soon step down.

The conflict between opposition fighters and regime forces has turned Syria into one of the world's worst humanitarian crises, exacerbated by attacks on aid workers, U.S. officials said Tuesday.

"There are 2.5 million people in need of aid now inside Syria, and 1.2 million have been displaced from their homes, so on that scale it's right up there with the worst crises in the world today," said David Robinson, a top official at the State Department's Bureau of Population, Refugees and Migration.

A top Syrian minister on Tuesday held out the prospect of strongman Bashar Assad stepping down as part of a negotiated settlement to 17 months of bloodshed that activists say has killed 23,000.

The comments from Syria's Deputy Prime Minister Qadri Jamil came following talks with Foreign Minister Sergei Lavrov and other Moscow officials who are keen to keep their sway over the Soviet-era ally in case of the fall of Assad.