Feb 3 (Reuters) - Russia's service sector contracted for the fourth consecutive month in January, a business survey released on Friday showed, as weak demand and an ongoing recession weighs on the industry.

The S&P Global Purchasing Managers' Index (PMI) for Russian services posted 48.7 for January, climbing from 45.9 a month earlier though staying below the 50-mark which separates expansion from contraction.

The sector has been under intense pressure since Russia sent tens of thousands of troops into Ukraine last February in what it calls a "special military operation".

A controversial mobilisation drive announced last September, which saw more than 300,000 Russian men drafted to the armed forces and hundreds of thousands flee abroad to avoid being conscripted, further sapped domestic consumer confidence and pushed the struggling services sector further into decline.

"The decrease in output stemmed from another monthly drop in new business amid weak domestic and international demand," S&P Global analysts said in a statement.

"The sustained decline in new orders led to a strong fall in backlogs of work. In turn, service sector firms cut their workforce numbers again," they added.

Russian services firms have cut employment in all but one of the last 14 months, according to the PMI data.

Businesses operating in the sector were also caught in a price squeeze, S&P Global noted, as the pace of rising input costs accelerated, while businesses' ability to raise their own prices dipped as they vied to stay competitive.

A sister survey on Wednesday showed Russian manufacturing output grew for the ninth month running in January. (Reporting by Jake Cordell; Editing by Toby Chopra)