Fighting intensified in Syria's two main cities on Tuesday, August 14 after rebels claimed they downed a government fighter jet and captured its pilot in what would be a major coup for the opposition, AFP reported

With Bashar al-Assad's embattled regime facing mounting diplomatic pressure, a top presidential aide was to hold talks in China, which has called for an immediate ceasefire and political dialogue to end the brutal 17-month conflict.

China and Russia are deeply at odds with the West over how to end the bloodshed, after both traditional Syria allies vetoed three UN Security Council resolutions, leaving the international community deadlocked on the crisis.

Bouthaina Shaaban, a "special advisor" to Assad, is to hold talks with Foreign Minister Yang Jiechi and other officials, the foreign ministry said, adding that Beijing was also considering inviting members of the Syrian opposition to visit soon.

UN humanitarian chief Valerie Amos is meanwhile due in Syria on Tuesday "to draw attention to the deteriorating humanitarian situation" and discuss ways of scaling-up relief efforts, her office said.

Many areas engulfed in the relentless fighting in Syria are also facing a desperate plight, suffering from food shortages, power outages and lack of medical supplies.