The U.N. refugee agency said Friday it is "very concerned" about the health of an American aid worker who was kidnapped in Pakistan.

The UNHCR said John Solecki suffers from a serious medical condition which may endanger his life. Spokesman Ron Redmond told reporters in Geneva that the United Nations is appealing to Solecki's captors to establish contact so that his release can be arranged.

Gunmen seized Solecki on Feb. 2 after shooting his driver to death as they drove to work in the southwestern city of Quetta.

The previously unknown Baluchistan Liberation United Front claimed responsibility in a telephone call to a Pakistan-based news agency. The name indicates the group is more likely linked to separatists than to Islamists.

Redmond said the U.N. has raised with government officials alleged discrimination against Pakistan's Baluch minority.

A week ago, Solecki's kidnappers threatened to kill him within 72 hours and issued a 20-second video of the blindfolded captive. It was unclear exactly when the deadline would expire.