Iran says it is holding the United States responsible for the lives of 48 Iranians kidnapped Saturday in Syria.

The state-run media say the foreign ministry told the Swiss envoy in Tehran that it expects the U.S. to use its influence to secure their release without any preconditions. Switzerland represents U.S. interests in Iran because Washington and Tehran do not have diplomatic relations.

Iran says the 48 abducted in Damascus were religious pilgrims, but a brigade commander with the rebel Free Syrian Army described them as elite Revolutionary Guards on a “reconnaissance mission.”

Iran's Foreign Minister Ali Akbar Salehi is visiting Turkey Tuesday to discuss the Syrian crisis with counterpart Ahmet Davutoglu.

Also Tuesday, Iranian state media said the secretary of Iran's National Security Council, Saeed Jalili, traveled to Damascus to meet with Syrian President Bashar al-Assad and other officials.

The Syrian government suffered a significant blow Monday when Prime Minister Riyad Hijab defected, two months after taking the top post. Riad Hijab said he was leaving what he called “the killing and terrorist regime.” Jordanian officials said he had defected to Jordan.

Meanwhile, Syrian opposition activists say government security forces are shelling neighborhoods in Aleppo Tuesday.

The Syrian Observatory for Human Rights said clashes were taking place in the city between rebels and Mr. Assad's forces.

Government and opposition claims in Syria are difficult to verify because journalists do not have a freedom of movement.