London police say they have conditionally released one of Pakistan's best known politicians but still are investigating him for alleged money laundering.

Saturday's release on bail of Altaf Hussain came four days after his arrest at his northwest London home. The 60-year-old spent three days in custody at a hospital receiving previously scheduled medical treatment, then faced police interrogation Friday.

The Metropolitan Police say Hussain must return for more questioning next month.

Hussain is the long-distance leader of the dominant political party in Karachi, Pakistan's largest city. His Muttahida Qaumi Movement frequently has been accused of threatening and killing political opponents. His party denies this.

Police say they are investigating the source of approximately 400,000 pounds ($675,000) seized last year during searches of London properties, including Hussain's home.