Riyad Hijab, the Syrian prime minister who fled to Jordan last week, declared in his first news conference in Amman on Tuesday that the Syrian government is falling apart and has ceded control of large parts of the country to rebel forces.

“The regime is collapsing, morally, materially and economically,” he said. “Militarily, it is crumbling, as it no longer occupies more than 30 percent of Syrian territory.”

It is next to impossible to confirm Hijab’s estimate of the scope of government-held territory, but President Bashar al-Assad’s forces on Tuesday still appeared to control most of Damascus and Aleppo, the country’s two largest cities.

Hijab is the most senior official to defect from Syria’s embattled government, and his escape has been widely seen as a strong signal that Assad is losing his grip. When news of his defection broke last week, the government said he had been fired.

But Hijab said at the news conference that he left while still in office and undertook a harrowing three-day journey to reach Jordan. And he openly pledged his support to the opposition.

“I won’t be anywhere but within the ranks of the people’s revolution, a loyal soldier, a defender of all the just demands of the revolution,” he said.

Meanwhile, opposition fighters were engaged in fierce street battles with government forces in Aleppo, Syria’s largest city and its commercial hub, and government planes bombed residential areas of the city, according to the Local Coordination Committees (LCC), an activist network.

The Syrian military said it destroyed seven rebel vehicles equipped with heavy machine guns and arrested “dozens of terrorists” in Aleppo, according to the official Syrian Arab News Agency. At least six people were killed in the fighting in the city on Tuesday, according to the LCC.

Also Tuesday, a video posted online purported to show the interrogation of a captured member of Lebanon’s Hezbollah movement who had come to Syria to fight in support of the government.

The video begins with three armed men standing behind the alleged Hezbollah member, who has a bruised face, as the man holding the camera shuffles through Lebanese ID cards.

The nervous captive says that his name is Hassan Salim al-Meqdad and that he is a sniper who came to Syria as part of a group of 1,500 Hezbollah fighters with clear instructions to support the Syrian military. “We must go in and help the regime of Syria,” he says.

Hezbollah said in a statement Tuesday that Meqdad is not a member of the movement.

In late May, a group of 11 Lebanese pilgrims was kidnapped in Syria while on the way back to Lebanon.

Al-Alam, the Iranian government’s Arabic-language satellite news channel, said Tuesday that one of its reporters, a Syrian national, had been kidnapped in the central Syrian city of Homs.

That report came 10 days after 48 Iranians were kidnapped in Syria’s capital, Damascus. The rebels say those Iranians are members of the elite Revolutionary Guard Corps, but Iran’s foreign minister, on a recent trip to Turkey to try to secure their release, said that while some of the captives are retired guard members, all of them had traveled to Syria on a religious pilgrimage.

The wave of kidnappings of Lebanese and Iranian nationals has been widely interpreted by analysts as a deliberate strategy by the rebels to pressure Hezbollah and the Iranian government, two of the Syrian government’s staunchest allies, to denounce Assad.

Suzan Haidamous and Ahmed Ramadan contributed to this report.