A rights group has reiterated calls for the release of popular Iranian rapper Toomaj Salehi, who was arrested during Tehran's clampdown on nationwide anti-government protests in October, due to his deteriorating state of health.

Salehi, 33, needs urgent medical treatment that cannot be provided in the prison, the New-York based Center for Human Rights in Iran (CHRI) said in a statement on April 6, citing sources close to the rapper.

In November, Iran's judiciary charged Salehi with spreading "corruption on Earth," a charge that could see him to sentenced to death.

Other charges against him include "propaganda activity against the establishment, forming an illegal group with the intention of disrupting the security of the country, cooperating with hostile governments, and spreading lies and inciting others to commit violence."

The prominent rapper strongly supported the nationwide protests sparked by the death in custody of 22-year-old Mahsa Amini, who was detained in September for allegedly violating the strict Islamic dress code for women.

"He is in urgent need of intense and coordinated international pressure for his freedom, as are the many other detainees and political prisoners in Iran," CHRI executive director Hadi Ghaemi said.

The CHRI says Salehi is being held in solitary confinement in the Dastgerd prison in central Iran.

Salehi's family expressed concern for his health after footage released by state media purportedly showed the rapper -- blindfolded, with bruises on his face, apologizing for his support of the protests.

The CHRI quoted a source close to Salehi as saying that he was "severely tortured" during the first days of his detention. The source, whose name was withheld over security concerns, said his left eye was badly damaged due to blows to the head and his right ankle was broken.

"We are very concerned about the severity and extent of his injuries," the source said.

Some 100 musicians, poets, artists, and activists called for Salehi release in November.

The rights group said Salehi has been denied a lawyer of his choice, leaving him unable to prepare a proper defense.

Thousands of people, including protesters, journalists, lawyers, athletes, and artists have been arrested and at least 537 people killed in Iran's brutal crackdown on the protests.

With reporting by AFP