Syrian troops and opposition forces have stepped up fighting close to Syria's second city, Aleppo. The confrontation follows a significant strategic victory by government forces in the border town of Qusair.
Reports from Syrian state television and the British-based activist group, the Syrian Observatory for Human Rights, indicated on Monday that fighting had erupted at a military airport about 30 kilometers (18.6 miles) from Aleppo.
"Opposition fighters have seized the radar tower in the Minnigh airbase," the Syrian Observatory for Human Rights director Rami Abdel Rahman told the news agency AFP.
However, Syrian state television reported late on Monday that Syrian troops had quashed the attack.
"Troops from our heroic army stopped terrorist groups from assaulting the Minnigh army airbase," the report said, according to the news agency DPA.
It was unclear when the battle had begun.
Many of last summer's most intense fights took place in Aleppo. The city has remained divided, some neighborhoods falling under the control of President Bashar al-Assad's government and others to opposition forces.
The clash on Monday came less than a week after Assad's army took the strategic border town of Qusair. That victory dealt a major blow to the rebels, who had been relying on the nearby highways as a key supply route to and from Lebanon.
Regaining control over the area underlined the Syrian government's military power and reminded international leaders - seeking to persuade President al-Assad to resign - that the rebels might lose.
The province of Aleppo lies in northern Syria and runs along its border with Turkey.
Kerry cancels Middle East trip
As violence intensified near Syria's second city, the US State Department announced that Secretary of State John Kerry had cancelled his trip to the region in order to attend meetings in Washington about the crisis in Syria.
"The intense preparations for a siege on the city of Aleppo only reaffirms the urgent need for the international community to focus its efforts on doing all we can do to support the opposition as it works to change the balance on the ground," US State Department spokesperson Jen Psaki told reporters.
The US has remained reluctant to send weapons to the Syrian opposition, instead supplying them only with "non-lethal" aid. However, growing evidence of the deployment of chemical weapons, compounded by the growing visibility of Hezbollah troops providing ground support to Assad have worried the Obama administration.
"The bloodshed and the loss of innocent lives has grown worse," Psaki said. "The increase of foreign fighters has led to a greater concern about sectarian violence. So we are taking a closer look at what we can continue to do to help the opposition."
According to the latest figures from the United Nations, more than 94,000 people have been killed since the civil war began over two years ago. The fighting and destruction have driven over 1.5 million people to seek refuge in neighboring countries.
kms/rc (AFP, Reuters, dpa)