GENEVA, Oct 26 (Reuters) - Fuel shortages in Yemen's besieged city of Taiz have forced one hospital to cut the number of incubators it can operate from 40 to 10, putting newborn babies at risk as weeks of fighting choke off vital supplies and deepen a humanitarian crisis affecting hundreds of thousands of people. "There's no oxygen, there's no fuel to run the incubators, to keep the babies warm," said Nada Ahmed, a nurse in the neonatal unit of the Yemeni-Swedish Hospital for Maternity and Childhood. Nawal Najeeb, a supervisor in the neonatal unit, warned the facility could be forced to halt operations if fuel supplies do not arrive. "It will be a catastrophe for the babies, a catastrophe of deaths and disabilities." Taiz has been largely isolated since October 3, with fightingpreventing humanitarian supplies from entering and civilians from leaving, following an escalation in clashes between the Saudi-backed government and the Iran-aligned Houthi movement.