Workers began a sit-in strike at Warsaw's main post Friday in a spreading pay dispute by postal employees that has made it difficult to pay bills, collect pensions and conduct other business.

The first Warsaw post office closed Tuesday, and by Thursday 38 of the 242 branches were on strike, according to official reports.Post offices also were closed in the southern cities of Krakow and Radom, where an official report said workers at 10 post offices were refusing to handle mail not labeled emergency.

Strikers are seeking wage increases and changes in working conditions at the offices, which provide a wide range of services including collecting rent and utility and insurance payments.