The Economic Planning Agency on Friday slightly upgraded its assessment of the domestic economy, saying it is continuing to improve moderately due largely to increased corporate activity.

"Activity continues to improve moderately thanks to the influence of various policy measures, the Asian economic recovery and gradual movements toward an autonomous recovery, mainly in the corporate sector," the EPA said in its monthly report for May.

The agency last upgraded its assessment of the economy in March, using the term "recovery" for the first time since the recession began in April 1997. It left its assessment unchanged in April.