Greece's jobless rate rose to 22.6 percent in the first quarter of 2012 from 20.7 percent in the previous three-month period as economic activity slumped, the country's statistics service said on Thursday.

It was the highest quarterly unemployment rate since this data series started in 1998. The jobless rate in the first quarter of 2011 was 15.9 percent.

Greece has already published monthly unemployment figures up to March. The quarterly data by the Hellenic Statistical Authority (ELSTAT) are based on a bigger survey sample and provide detailed figures for each sector of the economy. [Reuters]