CARACAS (AFP) - Several hundred doctors and medical students protested conditions in Venezuela's hospitals on Monday, citing shortages of medicines and critical supplies in the troubled oil-rich country.

As police held back the demonstrators in the city's Plaza Venezuela, other health workers marched without incident through the centre to the presidential palace in a government-organised show of support for President Nicolas Maduro.

The rival protests were the latest in an unresolved, nearly five-week-old crisis that has claimed the lives of at least 20 people.

Another victim was reported over the weekend in the western Andean city of Merida, Ms Giselle Rubilar, a 47-year-old Chilean national.

Chile's outgoing President Sebastian Pinera said in Santiago on Monday he had asked Venezuela to investigate her death of a gunshot wound to the head.

"Apparently there was a barricade near where she was living. She approached it and that's where she was reportedly hit by the bullet that caused her death," Chilean Foreign Minister Alfredo Moreno said.

Venezuelan doctors and medical students turned out in their white lab coats with signs denouncing the state of health care in the country.

"Not only bullets kill, the lack of medicine does too," read one sign.

The president of the Venezuelan Medical Federation, Dr Douglas Leon, said 95 per cent of hospitals have only five per cent of the supplies needed to take care of patients.

"The hospitals are deteriorated, supplies aren't available and we have to tell patients to buy their own," medical student Caterine Acosta, 20, told Agence France-Presse.

Meanwhile, at the Miraflores presidential palace, Mr Maduro touted the 2,500 medical students who he said will graduate this year from programmes in partnership with allies like Cuba.

Cuba provides an estimated 40,000 doctors and health care workers to staff clinics for poor and hard to reach populations in Venezuela.

In exchange, Venezuela supplies Cuba with 100,000 barrels of oil a day at preferential rates.