European Union leaders demanded the immediate release and rehabilitation of Belarus political prisoners in a joint statement issued Friday at the close of a summit with ex-Soviet states in Warsaw.

Expressing "deep concern" at the deteriorating human rights situation in the country, the 27 EU leaders "call for the immediate release and rehabilitation of all political prisoners", the statement said.

The bloc also noted its concern over reports that prisoners are being denied access to lawyers and their relatives as well as to medical care "while being put under psychological and physical pressure."

The statement was issued as Belarus boycotted the Eastern Partnership summit over pressure applied by Europe on authoritarian leader Alexander Lukashenko for throwing hundreds of opponents behind bars.

The chair of the Belarus delegation at the summit table stood empty after EU leaders attending the talks warned the door would be closed on new trade and aid deals until Lukashenko ended his heavy-handed crackdown against regime dissidents.