Syria's army launched multiple attacks on rebel positions on Tuesday in the northern province of Aleppo, including insurgent-held areas of a key airbase, a monitoring group said.

Syrian government forces shelled parts of the Minnigh military airbase a day after rebels seized its strategic radar tower, months into a battle for the site in northern Syria, the Syrian Observatory for Human Rights said.

Twin suicide attackers targeted a police station in central Damascus killing at least 14 people and wounding more than 30, state television and a watchdog said.

The broadcaster screened images of blood and broken glass on the pavements near the scene of the blasts.

Syrian rebels have clashed with government troops after converging on a military airport in Aleppo, a monitoring group and state media said, as the United States said it was considering "all possible options" to help the opposition.

Buoyed by victory in the strategic town of Qusayr on the border with Lebanon, President Bashar Assad's troops have been readying to open a northern front in Aleppo province on the border with Turkey.

Iran is working round the clock to enlarge its nuclear infrastructure with the eventual aim of developing an industry capable of building up to 30 bombs a year, an Israeli minister charged on Monday.

Speaking to reporters in Jerusalem, Intelligence Minister Yuval Steinitz said Tehran was "very close" to crossing the red line laid out by Israeli Prime Minister Benjamin Netanyahu last year.

A wave of attacks on Monday, mostly against Sunni areas of Iraq, killed 70 people in renewed bloodshed that, coupled with widespread political paralysis, has revived fears of all-out sectarian war.

The violence, which left more than 230 people wounded, came after several days of relative calm following symbolic moves by Iraq's political leaders to ease tensions among the country's communities after the U.N. warned violence was ready to "explode".

Palestinian preconditions for peace talks make a return to negotiations impossible for Israel, Prime Minister Benjamin Netanyahu said on Monday.

"To me the setting of preconditions is an insurmountable obstacle," Netanyahu told the foreign affairs and defense committee, a parliamentary statement said.

Syrian President Bashar Assad may succeed in crushing the two-year-old uprising against his rule with the support of Iran and Hizbullah fighters, Israel's intelligence minister said on Monday.

"It might be the case that, at the end of the day, Assad .. might get the upper hand," he told a meeting of the Foreign Press Association. "I think that this is possible.

Twenty victims of a deadly 1988 gas attack on Iraq's Kurdish town of Halabja filed a complaint in Paris Monday in a bid to shine the light on firms that helped Saddam Hussein's regime build a chemical arsenal.

Four of the victims made the trip, two of whom suffer from severe respiratory problems since the bombing which killed some 5,000 Kurds, in what is thought to have been the worst ever gas attack targeting civilians.

Syria's main opposition group lashed out Monday at the execution a day earlier of a 15-year-old child at the hands of unidentified Islamist gunmen who accused him of blasphemy.

"The National Coalition condemns every act that violates the Syrian people's values and the principles of the (rebel) Free Syrian Army," the group said in a statement.

A young Belgian man has been killed in Syria while fighting for an Islamist group and his brother was arrested on his return home from the war-stricken country, newspapers said Monday.

Belgian authorities and Islamic groups have become increasingly concerned about a growing number of young men leaving to fight in Syria against the regime of President Bashar Assad, some of whom are suspected of war crimes.