PKR de facto leader Anwar Ibrahim was rushed to hospital due to high blood pressure, his lawyer Sivarasa Rasiah said.

Sivarasa, who is Subang MP, said Anwar's blood pressure has been "unstable".

"Let us all pray for him," he said in a Facebook posting.

Anwar is serving a five-year jail sentence for Sodomy II at the Sungai Buloh prison.

He was convicted of sodomising his aide Mohd Saiful Bukhari Azlan.

The Federal Court upheld his conviction in February last year.

Anwar's family had earlier claimed he did not receive sufficient medical attention, including for injuries sustained before imprisonment.

However, the Health Ministry said the politician has been assessed and treated by a panel of specialists.

The Home Ministry also said that he is given special concessions including hot showers, a bed which fits the specification of a high-end hospital to account for his bad back and milk and cereal to meet special dietary requirements.