Iran said on Tuesday that it was holding the United States responsible for the lives of 48 of its citizens taken hostage in Syria, following an unconfirmed report by a Syrian rebel group that three of them had been killed by shelling.

The foreign ministry, which transmitted its message through the Swiss embassy in Tehran that handles U.S. interests in the absence of Iran-U.S. diplomatic relations, insisted the 48 were pilgrims, not Revolutionary Guards as the rebels claimed.

The defection of Syria's prime minister shows President Bashar Assad has lost control of the country and that his people believe his days are numbered, U.S. officials said Monday.

Prime Minister Riad Hijab slipped across the border into Jordan on Sunday night and announced he was joining rebels in the highest-ranking defection of the 17-month uprising against Assad's rule.

The families of the 11 Lebanese Shiite pilgrims who were abducted in Syria on Monday blocked the airport road to protest the Lebanese state's failure to secure their release.

State-run National News Agency said the protesters used their cars and motorcycles to block the highway in both directions.

Former prime minister Saad Hariri said a visit on Monday to Lebanon by Saeed Jalili, head of Iran's Supreme National Security Council, was “unwelcome in this critical period during which the Syrian people are suffering the most horrible types of massacres and destruction at the hands of Bashar Assad’s regime and its foreign protectors.”

“This visit also contradicts with the interest of the Lebanese people who cannot dissociate themselves from showing solidarity with their brothers in Syria or from the unified Arab stance demanding the resignation of Bashar Assad and an end to the Iranian regime’s interference in the Arab affairs in general and the Syrian and Lebanese affairs in particular,” Hariri added in a statement.

Iran is to hold a ministerial meeting on Thursday for countries having a "realistic position" on Syria, Deputy Foreign Minister Hossein Amir Abdollahian said, the official news agency IRNA reported.

He said 10 countries would be participating, but did not identify them.

Germany said Monday that the defection of Syrian prime minister Riad Hijab pointed to the rapid "erosion" of the regime of President Bashar Assad.

"The reports show how far the erosion process of the Assad regime has progressed," Foreign Minister Guido Westerwelle said in a statement.

Progressive Socialist Party leader MP Walid Jumblat praised on Monday President Michel Suleiman’s “important political positions” on Army Day, most notably his remarks that “there can be no partnership with the army and forces responsible for maintaining Lebanon’s security.”

He said in his weekly editorial in the PSP-affiliated al-Anbaa magazine: “We are seeking arms for the defense of Lebanon alone. We don’t want a defense strategy for the Hormuz Strait or any other area.”

Israel has improved the accuracy of its Arrow 2 missile interceptor system, including its ability to intercept medium-range missiles present in the arsenals of Iran and Syria, media reported on Monday.

The new system, known as "Block 4," will be installed in missile batteries in the coming weeks, reports said.

Syria's exiled opposition accused the government on Monday of killing 40 people in a massacre in a central town in a bid to terrorize people into flight to change the confessional balance of the region.

The Syrian National Council said that a further 120 people were wounded in the attack by troops and militia on Harbnafsa, in Hama province, a town of some 8,000 inhabitants.

A bomb blast rocked the headquarters of Syrian state television in the heart of Damascus on Monday wounding several people, Information Minister Omran al-Zoabi said.

"It is clear that the blast was caused by an explosive device," Zoabi said. "Several of our colleagues were injured, but there were no serious injuries, and no dead."