CHICAGO (Reuters) - Sears Holdings Corp <SHLD.O> said on Thursday it was shuttering 103 unprofitable Kmart and Sears stores as it continues to streamline operations amid mounting debt and a string of quarterly losses.

The department store operator, which has racked up 24 straight quarters of sales declines, said 64 Kmart stores and 39 Sears stores would be closed between early March and early April this year.

Sears Holdings, once the largest retailer in the United States, said at the end of October that it operated 1,104 stores, nearly half the 2,019 stores it ran in 2012.

The closures announced on Thursday were in addition to 63 stores Sears is closing this month, having also shuttered 330 stores in 2017.

Shares in Sears closed down 4.8 percent on Thursday.

Liquidation sales will begin as early as Jan. 12 at the closing stores, Sears said, adding that "eligible" staff at these stores would receive severance.

Company spokesman Chris Brathwaite declined to disclose the number of jobs that would be cut, but said an overwhelming majority of them were part-time positions. He added that only full-time employees typically received severance packages, but that this would vary depending on local laws.

Sears' billionaire chief executive and biggest shareholder Eddie Lampert said in July that some vendors had reduced their support, placing additional pressure on operations. In October, Whirlpool Corp <WHR.N>, one of Sears' biggest vendors, said it would stop supplying some big name-brand appliances to the department store chain.

Lampert is also among Sears' biggest lenders through his hedge fund, ESL Investments.

(Reporting by Richa Naidu; Editing by Tom Brown and David Gregorio)