The International Committee for the Red Cross warned on Thursday that the humanitarian situation in Syria has deteriorated sharply amid intensified fighting in several parts of the country between government forces and rebel groups, as well as among rival opposition faction.

The ICRC statement came after a two-day visit of the agency's director of operations, Dominik Stillhart, to the Syrian capital, Damascus, where he met government officials, appealing for more access to areas affected by the fighting, including the violence-torn, besieged Palestinian refugee camp of Yarmouk.

The camp has been the scene of clashes between local fighters and the Islamic State group since the beginning of April. It was the latest tragedy to engulf the camp's residents, who have already suffered through a devastating two-year government siege, starvation and disease.

About 18,000 people are still in the camp, a built-up area once home to some 160,000 Palestinians and Syrians. The United Nations over the weekend expressed alarm over the continued fighting, along with use of heavy weapons, and airstrikes.

Fighting has also intensified elsewhere in Syria in recent weeks, as rebel advances have pushed out government forces from contested areas in the country's south and north. Government troops are pushing back.

On Thursday, Syrian government forces and allied fighters from the Lebanese Hezbollah group took control from Islamic militant fighters of more areas near the Syrian border town of Assal al-Ward.

Al-Manar TV, affiliated with Hezbollah, said dozens of militants were killed or wounded. The Britain-based Syrian Observatory for Human Rights said intense shelling and airstrikes in the area caused casualties on both sides.

"The fighting is escalating in many parts of the country and more and more people are being forced to flee their homes. It is causing untold suffering," said Stillhart, the ICRC director.