Syria has resumed an aerial attack on the opposition-held town of Ras al-Ain, near the border with Turkey, dropping two bombs on a Syrian security building that had been captured by the opposition forces, according to an official from the mayor's office in the Turkish border town of Ceylanpinar.

Turkish ambulances rushed to the border on Monday and at least 11 wounded Syrians were brought to the hospital in Ceylanpinar for treatment.

Shrapnel from the bombing landed on Turkish territory, but no one was injured, officials said.

The official spoke on condition of anonymity in line with Turkish government rules that prevent civil servants from speaking to journalists without prior authorization.

The attacks came a day after Syrian fighter jets and artillery blasted parts of the capital, Damascus, and its suburbs on Sunday.

Also on Monday Fierce fighting erupted in the Aleppo district of Bustan al-Basha on Monday as troops advanced for the first time into the stronghold of opposition fighters, a military source and resident told AFP.

The Syrian troop advance came on the fourth day of fighting in the northern district, which has been controlled for months by opposition forces from the opposition battalions of Al-Nusra Front and Ahrar al-Sham.

The resumed bombings also coincided with Russian President Vladimir Putin's trip to Istanbul.

Russia and China have used their veto power at the UN Security Council to block any sanctions imposed on President Bashar al-Assad's regime over its crackdown on the uprising that began in March 2011.

The UN also said on Monday that it was suspending its aid operations in Syria and withdrawing all non-essential international staff due to the worsening security situation.

Against this backdrop, the Syrian foreign ministry said in a statement on state television on Monday that the government would not use chemical weapons, if it had them, against its own people.

"In response to the statements of the American secretary of state, who warned Syria against using chemical weapons, Syria has stressed repeatedly that it will not use these types of weapons, if they were available, under any circumstances against its people," the statement said.

According to activists, at least 40,000 people have been killed since March 2011.

PHOTO CAPTION

Syrians cross the border from Syrian town of Ras al-Ain to Turkish border town of Ceylanpinar after an air strike, December 3, 2012.

Aljazeera