The Red Cross has appealed for a halt in the fierce fighting between President Bashar al-Assad's forces and rebels in the Syrian city of Homs, to bring in life-saving supplies to trapped residents.

The International Committee of the Red Cross (ICRC) said thousands of Syrian lives were at risk in the old city of Homs, where Assad's forces have been pushing a heavy offensive with air and artillery strikes to try to retake rebel areas.

The Red Cross said combatants in the more than two-year conflict were hampering the delivery of aid to beleaguered locals and had failed to secure safe passage for trapped residents trying to flee the area.

"We call on the Syrian authorities to permit delivery in the old city of food and medical supplies," said Magne Barth, the head of the ICRC delegation in Syria.

"We also call on all the armed groups that are in control of the old city to ensure that civilians who want to leave can do so safely."

Syria's uprising-turned-civil war has become increasingly violent, killing more than 100,000 people so far.

International powers at the U.N. Security Council are deadlocked over how to find a diplomatic solution. China and Russia, Assad's main arms supplier, have blocked efforts to sanction Assad by the United States and Europe, who back the rebels.

Homs is the epicenter of the armed insurgency that grew from popular street protests struggling to end more than four decades of Assad family rule.

Intense battles previously fought in the divided city have flattened several districts and made it increasingly challenging for aid workers to reach trapped civilians.

Combatants on both sides have attacked and killed volunteers from the Syrian Arab Red Crescent, the local partner for the ICRC.

Aside from the thousands who have died, aid groups estimate there are nearly 4 million people displaced by the violence inside Syria, many of them penniless and in desperate need of aid.

"Should we receive the consent necessary, we will pursue our efforts to bring humanitarian assistance into the old city, provided the partners to the conflict agree to a humanitarian pause in the fighting, to ensure safe access for the teams from the ICRC and the Syrian Arab Red Crescent," Barth said.-Reuters