Updated

A pan-Arab television station aired a video Sunday purporting to show Syrian rebels guarding a group of Iranians abducted a day earlier and promising more attacks on Iranian targets.

Armed men in the video identify themselves as members of the rebel "Baraa Brigades" and say that at least one of the 48 captives was an officer of Iran's powerful Revolutionary Guards. They claim they Iranians were on a "reconnaissance mission" in the capital Damascus at the time they were abducted. Iran says they are pilgrims who were visiting a shrine.

"We promise Iran and all those who support this regime ... we will strike at all (Iranian) targets in Syria," one of the rebels says in the video. "The fate of all Iranians who operate in Syria will be the same as those we have here, either captive or killed, God willing."

The abductions threaten to pull Syria's close ally Iran deeper into the country's civil war. They also raised questions about the extent to which President Bashar Assad's regime can control the center of its power in the capital.

Last month, rebels and Syrian regime forces fought intense battles for a week in Damascus, the opposition fighters' biggest challenge so far in the capital.

The government claimed Saturday it was now in full control of all districts in Damascus after purging one of the last rebel-held areas. But several residents reported hearing loud explosions and gunfire from several districts of the capital throughout the night.

Gunmen snatched 48 Iranian pilgrims just outside Damascus on Saturday in a brazen attack. The pilgrims were on a bus taking them from the suburb of Sayeda Zeinab, about 10 miles south of Damascus, to the airport to return home when they were kidnapped, according to the Iranian state news agency, IRNA.

Mainly Shiite Iran is a close ally of the beleaguered Syrian government, which is dominated by the minority Alawite sect, an offshoot of Shiite Islam. Syria has long welcomed Iranian pilgrims visiting the ornate, gold-domed shrine of Sayeda Zeinab, the Prophet Muhammad's granddaughter.

But the rebels in the video claimed there was an officer in Iran's Revolutionary Guard among the group and showed what was purportedly his ID and a permit to carry weapons.

IRNA said Sunday that Iranian Foreign Minister Ali Akbar Salehi had spoken by phone with his Turkish and Qatari counterparts and demanded their intervention to help release the Iranians. Turkey and Qatar have supported the overwhelmingly Sunni Muslim rebels in Syria.

The Turkish and Qatari foreign ministers promised to make efforts for the release of Iranian pilgrims, IRNA reported Sunday.

In Tehran, a senior member of an influential parliamentary committee advised Iranians against traveling to Syria, state-run Press TV reported, in a high-ranking acknowledgment that Syrian rebels have expanded their hold over key roads and other areas once firmly under Assad's control. The comment by Kazem Jalali, a member of Iran's Committee on Security and Foreign Policy, does not represent an official Iranian discouraging travel to Syria, but the views of the parliament group often shape policies.

U.S. Secretary of State Hillary Rodham Clinton will visit Istanbul later this week for talks with Turkish officials over the worsening crisis in Syria, the State Department said Sunday. Turkey, which has taken in tens of thousands of Syrian refugees, has beefed up its military presence along the border.

The main battle in the civil war has now shifted to Syria's largest city, the commercial hub of Aleppo, some 215 miles north of Damascus. Rebels seized several neighborhoods there two weeks ago and the regime has struggled to dislodge them ever since in a stark demonstration of the rebels' growing strength and organization and the regime's loosening grip on the country

On Sunday, Syrian opposition groups and activists said fierce clashes were still ongoing as rebels tried to expand their hold and inch closer to the historic city center.

Local activist Mohammad Saeed said there is fighting only a few hundred yards from the medieval citadel overlooking the city center. Heavily armed government troops have been steadily shelling rebel-controlled districts, mainly in the southwestern part of the city, for the past two weeks.

Saeed and the British-based Syrian Observatory for Human Rights reported heavy shelling and clashes Sunday mainly in the districts of Salaheddine, al-Sukkari and Hananou.