(Adds details and quotes, ICRC statement, byline)
By Stephanie Nebehay
GENEVA, Aug 7 (Reuters) - Many of the main drugmakers in conflict-torn Syria have closed down, causing severe shortages of medicines for treating chronic diseases and a rising number of casualties, the World Health Organization (WHO) said on Tuesday.
Hospitals or health centres have stopped functioning due to a lack of staff or supplies, while others have been damaged or taken over by fighters, the U.N. agency said.
Before the 17-month-old revolt against President Bashar al-Assad, Syria produced 90 percent of its medicines and drugs. But production has been hit by the fighting, lack of raw materials, impact of sanctions and higher fuel costs, it said.
"We are receiving more and more reports of shortages in medicines and pharmaceutical products in Syria," WHO spokesman Tarik Jasarevic told a news briefing.
Ninety percent of Syria's pharmaceutical plants are located in rural Aleppo, Homs and Damascus provinces and they have suffered substantial damage from the latest fighting, he said.
"Many of these plants have now closed down as a result of the ongoing clashes and increased cost of fuel, resulting in a critical shortage of medicines," he said.
Drugs for tuberculosis, hepatitis, hypertension, diabetes and cancer are urgently needed, as well as dialysis equipment to treat kidney disease, according to the WHO.
"The impact of this situation is of course devastating for people who need drugs on a daily basis, people with chronic conditions, people with a mental health situation, and also for people who are on antibiotics to prevent infections when being treated for conflict-related injuries," Jasarevic said.
The WHO has delivered surgical and trauma kits, and medical supplies for 700,000 people. It has no estimate for the number of wounded or hospitals still open in the country of 22 million where an estimated 18,000 have been killed in the conflict.
"Health facilities that have stopped functioning are located in the most affected areas where the urgent need for medical and surgical interventions is the most prominent," Jasarevic said.
"We are bringing in medical supplies, but this cannot cover the needs of such a big country and cannot cover the gap left by this closing down of the pharmaceutical industry," he said.
The Syrian health ministry has reported that it has lost 200 ambulances over the last few weeks, mainly vehicles destroyed or no longer under its control, Jasarevic said.
The heightened violence has recently spread to the two largest cities, Aleppo and the capital Damascus, exacerbating the humanitarian crisis. Rebels trying to fight off an army offensive in Aleppo said on Tuesday they were running low on ammunition as Assad's forces encircled their stronghold at the southern entrance to the country's biggest city.
The International Committee of the Red Cross said on Tuesday that medical items to treat 500 wounded in Damascus had been delivered via the Syrian Red Crescent over the past four days.
The U.N. World Food Programme, which had hoped to provide 850,000 Syrians with food by the end of July, managed to reach only 542,000, WFP spokeswoman Elisabeth Byrs told reporters.
It has sent rations for 46,000 people to Aleppo and aims to reach 28,000 more in coming days to cover food shortages, she said.
Around 124,000 Syrians have fled across the borders and registered as refugees, while 1.5 million are estimated to be displaced within Syria.
(Reporting by Stephanie Nebehay; Editing by Mark Heinrich and Roger Atwood)