Half a million people across war-hit Syria have been wounded, many of them lacking access to basic healthcare and treatment, the International Committee for the Red Cross said on Sunday.
Millions have also been displaced inside Syria and tens of thousands detained, ICRC chief Magne Barth said in a statement.
"At least half a million people have been wounded across the country and millions remain displaced and tens of thousands detained," he said.
"The wounded are often not cared for properly and the chronically ill often do not receive the treatment they need," Barth added.
The ICRC urged again the Syrian government and the rebels to allow humanitarian assistance to reach all people affected by the 33-month conflict.
Barth said Syrian authorities were preventing access to rebel-held areas besieged by loyalists troops, including in Homs and Damascus provinces, despite saying more humanitarian assistance was needed.
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"Our staff are still not allowed to enter besieged areas to deliver aid, including much-needed medical supplies, to all people in need whoever they may be," said Barth.
The UN World Food Programme (WFP) said on Monday that half of Syria's population of around 23 million is "food insecure" and nearly a third needs urgent assistance.
"Recent assessments show that almost half the population inside Syria is food insecure and close to 6.3 million people need urgent, life-saving, food assistance," WFP said in a statement.
Activists in besieged areas have given harrowing accounts of hunger and a lack of medicine and equipment to treat the sick and wounded.
The ICRC said a harsh winter that hit the region earlier than expected this year has added to the "misery" of millions of Syrians displaced internally and refugees sheltering in neighbouring countries.
The Syrian Observatory for Human Rights says that more than 126,000 people have been killed in Syria since the conflict erupted in mid-March 2011 and millions more forced to flee their homes.
The ICRC says 32 volunteers who worked for the Syrian Red Crescent are among the dead.