The United Nations mission in Syria says its observers have witnessed government fighter jets opening fire on Aleppo, the country’s largest city.

In a briefing on Wednesday, mission spokeswoman Sausan Ghosheh also said the UN had confirmation that the rebels now have heavy weapons of their own, including tanks.

Ms. Ghosheh expressed concern over the situation in the northern city of Aleppo, where rebels have been battling government forces for the past 12 days.

She described “heavy use of heavy weapons, including tanks, helicopters, heavy machine guns, as well as artillery.”

Assad urges army to step up fight

Meanwhile, in a statement to the army, Syrian President Bashar Assad urged his armed forces to step up the fight against rebels as a 17-month-old uprising continues to rage across the country.

Mr. Assad has not spoken publicly since a bombing killed four of his top security aides two weeks ago. Wednesday’s written statement was carried by the state-run news agency.

“In the war in which the country is embroiled and the battle against criminal and terrorist gangs, the army has proven its mettle,” he said, adding that the Syrian people have shown themselves not easily “tamed” by foreign plots.

Mr. Assad was speaking to the army on the 67th anniversary of its founding. He called it the “homeland’s shield” against foreign plots. “I have great confidence in you and the masses see you as a source of pride and honour ... and a defender of just causes,” he said.

While there have been many defections from the rank and file and even a few generals, Syria’s armed forces for the most part have remained cohesive. Supported by heavy weapons, they have been slowly regaining momentum against the rebel army.

More In: International | News