WORCESTER (AP) -- A Central Massachusetts hospital system has announced that it is either eliminating or reducing hours for almost 100 positions as a way to rein in costs.

UMass Memorial Health Care said in a statement Wednesday that more than 300 positions at the company's Worcester-based operations have been affected since October, including 99 this week. The positions are from a number of levels, including vice presidents, directors, managers and clinical staff.

Nearly a third of the 99 positions have been vacant since a hiring freeze was implemented several months ago.

The cuts are part of a plan to offset an operating loss of about $55 million in the 2013 fiscal year.

The system runs five hospitals -- UMass Memorial Medical Center in Worcester, HealthAlliance of Leominster, Marlboro Hospital, Clinton Hospital and Wing Memorial Hospital in Palmer -- and a doctors' group. It employs about 13,000 people.