The UN High Commission for Human Rights said on Friday that it was \"extremely concerned\" about the human rights and humanitarian impact of a recent major offensive launched by the Syrian government to retake several opposition-controlled districts in Homs. \"According to information just received, the Al-Khaldiya neighbourhood has been experiencing heavy shelling since the early hours of this morning. These attacks are now affecting all of old Homs district\", said the Spokesperson for the UN High Commissioner for Human Rights Rupert Colville in a press briefing. Although the total number of casualties remains unknown, the number of civilians currently trapped due the heavy fighting in and around Homs is believed to be between 2,500 and 4,000 people. Shortages of food, water, medicine, electricity and fuel in besieged areas are severely affecting civilians, including women and children. The siege began 13 months ago but has escalated since June 28. Out of 16 residential districts affected by the ongoing siege, shelling and ground attacks in Homs and in the surrounding area, Al-Khaldiya and Baba Houd districts appear to be the worst hit. Recent reports suggest that armed opposition groups are operating inside those residential areas, thereby increasing the risk for civilians. We call upon all parties to respect their obligations under international law, avoid civilian casualties and allow trapped civilians to leave without fear of persecution or violence. We also call for unrestricted and immediate humanitarian access to all conflict-affected populations in besieged areas.