Rebels in Syria on Thursday bombarded the Menagh air base that was being used by helicopter gunships and other warplanes to attack the northern city of Aleppo, sources said.

Syrian rebels used tanks to attack a military airport northwest of Aleppo on Thursday, a rebel commander said, as a human rights group reported 67 people killed in violence nationwide.

"We had already attacked the airport several times, but this was the first time we used heavy weapons," which were "four tanks taken from Anadan," rebel commander Abdel Aziz Salameh told Agence France Presse, referring to a strategic military checkpoint outside Aleppo that the rebels captured on Monday.

Tehran is demanding the immediate release of a group of Iranian Red Crescent workers kidnapped in Libya, and says the Libyan government is responsible for their lives, the ISNA news agency reported on Thursday.

"Iran demands immediate action to free the seven members of the Iranian Red Crescent," deputy foreign affairs minister Hossein Amir Abdollahian was quoted as saying.

The U.S. Congress Wednesday approved punishing new sanctions targeting Iran's energy and shipbuilding sectors, a day after President Barack Obama unveiled measures to cripple Tehran's nuclear drive.

The House of Representatives voted overwhelmingly 421-6 for the measure, which Foreign Affairs Committee chair Ileana Ros-Lehtinen described as the toughest sanctions yet imposed on the Islamic republic over its refusal to rein in its nuclear program.

President Barack Obama has signed a covert document authorizing U.S. support for Syrian rebels locked in a battle to overthrow beleaguered President Bashar Assad, reports said Wednesday.

The directive was contained in a "finding" -- a device authorizing clandestine action by the Central Intelligence Agency, NBC and CNN said, citing unidentified sources.

The United States Wednesday denounced Syrian President Bashar Assad as "cowardly" and "despicable" for calling on his forces to continue the fight against opposition rebels.

"We think it's cowardly quite frankly to have a man who's hiding out of sight be exhorting his armed forces to continue to slaughter the civilians of his own country," said a U.S. State Department spokesman, Patrick Ventrell.

France will seek to organize a ministerial-level U.N. Security Council meeting on Syria before the end of August, Foreign Minister Laurent Fabius said in a statement on Wednesday.

France currently holds the rotating chair of the Security Council and Fabius had said on Monday that Paris would try to organize a meeting before the end of this week.

Angry Muslims attacked a church and Christian homes outside Cairo on Wednesday, sparking clashes that wounded 16 people, a security official said, after a Muslim died of wounds from a fight with a Christian.

Police fired tear gas to prevent the mob setting fire to the church but the crowd returned and torched several homes in the village of Dahshur as well as three police cars, the official said.

Bahraini police have arrested three suspects over "terrorist activities" after seizing materials that can be used to manufacture explosives, the public security chief said on Wednesday.

Major General Tariq al-Hassan said in remarks to the press that police are still searching for three other suspects.

President Vladimir Putin will strongly defend Russia's position on the Syria conflict when he meets British Prime Minister David Cameron in London on Thursday, his spokesman said.

"We expect to have another opportunity to continue our dialogue and explain to the British side our well-argued, consistent and absolutely clear position on the (Syria) problem," spokesman Dmitry Peskov told Russian news agencies.