Syrian rebels drew criticism for images like this one from Aleppo on Tuesday in which they dragged a suspected pro-government militiamen into the street.
BEIRUT, Lebanon — Syria’s rebels shelled an airport near Aleppo on Thursday in what was described as one of the first known instances of insurgents using captured heavy weapons, as opposition activists warned that fighting for the city, the country’s main commercial center, would likely intensify.
A Syrian activist said President’s army appeared to be preparing for an all-out assault.
“We have seen military reinforcements making their way to Aleppo,” said Abou Firas, an activist in Aleppo using a satellite Internet connection because telephone and Internet service from the city was cut off. “We were worried about massacres but now we are issuing a warning about a war of extermination to be launched by the regime.”
The news about the government reinforcements could not be independently confirmed because of restrictions on reporters. It came after the battle for Aleppo intensified on Wednesday when United Nations observers there reported that Syrian jets had fired rockets into contested neighborhoods and that rebels had commandeered tanks and other heavy weapons.
The opposition Syrian Observatory for Human Rights, based in Britain, said the rebels had put the captured armor to use, shelling a military airport near Aleppo.
A video forwarded by Mr. Firas, purportedly from a highway between Aleppo and the coast, showed a convoy of nearly a dozen tanks, gas tankers, and several pick-up trucks carrying armed soldiers.
It was not clear when the video was shot, but before earlier ground assaults, the Syrian government has cut off communication in what appears to be an effort to keep rebels — who have become extremely savvy with YouTube videos and Skype — from broadcasting the army’s attacks.
By Thursday afternoon in Syria, the Syrian Observatory for Human Rights said the Internet was coming back online gradually. Clashes continued, especially in the southwest of Aleppo, where rebels and Syrian troops have been engaged in a bitter battle for control.
Some reports from Turkey also suggested that government forces were trying to cut rebel supply lines, with fighting raging in a rebel-held town near the Turkish border.
On Wednesday, hours after President Assad urged his forces to step up the fight, opposition leaders said they had found dozens of bodies in a suburb of Damascus in the aftermath of the Syrian Army’s house-to-house search for rebel fighters and activists. This claim of a new massacre came as the rebels faced severe criticism themselves for what appeared to be their brutal summary execution, one day earlier, of suspected pro-government gunmen on the streets of Aleppo, recorded and uploaded on the Internet.
Videos purported to have been taken in the Damascus suburb, Jdeidet Artouz, showed bodies lined up under bloodstained sheets, as a narrator gave an estimated count that continued rising: 37, 42, and then even more.
“I counted 52 bodies,” said Abu Abdullah, a resident who said he had helped move the dead to a local mosque before burial. “I’m really shocked. Why here?”
The bodies were found near an area where rebels said fighting had flared in the past week. But analysts said the bodies appearing outside Damascus in a town also filled with refugees — along with reports of renewed fighting in the capital and an escalation of combat in Aleppo, Syria’s largest metropolis and commercial center — all suggested that the 17-month-old conflict was becoming increasingly intense and bitter, with more front lines and more bloodshed.
“It’s a rapid escalation,” said Andrew J. Tabler, a senior fellow at the Washington Institute for Near East Policy. “Once you start using fixed-wing aircraft and you have a city under full revolt, it’s clear that the Assad regime is not going to stop and is not breaking. We’re entering a new phase of this conflict.”
Aleppo, which for much of the anti-Assad uprising had been relatively stable, now is the site of the most vicious fighting. For nearly two weeks, the Syrian Army has been battling rebel troops for control of the city, and for the first time, the United Nations said on Wednesday what rebels had been saying for days: the Syrian Army was using jet fighters in its arsenal of heavy weapons aimed at crushing the opposition. And they are not just flying, as in the past; now, according to the United Nations monitor mission in Syria and videos showing flashes of light bursting from dark jets, they are firing.
“Our observers confirmed fighter aircrafts firing rockets and cannons — heavy machine-gun fire,” said Sausan Ghosheh, a spokeswoman for the United Nations monitor mission.
Mr. Tabler noted that the Syrian warplanes were not yet dropping bombs. But the calculated escalation in the use of jets seemed to be part of a concerted effort by Mr. Assad to rally his supporters by making clear that he would not limit his military effort. In rare published remarks seemingly designed to marshal government forces and dissuade anyone thinking of defecting, he called on Syria’s military to show “more readiness and continued preparations” to confront “internal agents” seeking to destabilize his battered country, according to the official SANA news agency.
This week, it has become increasingly clear to outside military analysts that the fighting is likely to drag on in Aleppo. Helicopters thwacked overhead Wednesday as clashes broke out around several more police stations, which have become a focal point for rebels seeking to hold neighborhoods or gain ground.
Taxi drivers skittered down streets charging four or five times the usual fare, while residents said water, food and electricity seemed ever scarcer.
With the rebels now possessing tanks — United Nations observers did not have information on how many, or where they might be deployed — the conflict seems to be moving ever further away from the six-point plan for peace outlined by Kofi Annan, the special Syria envoy for the United Nations and the Arab League, whose plan seems increasingly irrelevant. Instead of steps toward a cease-fire, both sides appear to be rushing into the breach of civil war.
Opposition figures drew special attention to the bodies in Jdeidet Artouz — sending an alert to reporters with a link to live-streaming video of a mass funeral procession and mass burial — just one day after rebels in Aleppo caused an outcry among rights groups and others over their videotaped public executions of men identified as pro-government militiamen.
Those executions attracted hundreds of thousands of views on YouTube, and were cited by Russia, the Syrian government’s most important foreign backer, as evidence of brutality by Mr. Assad’s armed adversaries, whom he calls terrorists.
“Bloody reprisal of the opposition forces over the government supporters in Aleppo proves that human rights are violated by both sides,” said Gennady Gatilov, the deputy Russian foreign minister, in a Twitter message.