Pakistani police have arrested an ethnic Pashtun rights activist and charged him with hate speech after he spoke during a visit to neighboring Afghanistan.

Police official Usman Wazir said Sardar Arif Wazir, a member of the Pashtun Tahafuz Movement (PTM), was arrested on April 17 in South Waziristan, a tribal region located along the border with Afghanistan.

The police official said Wazir was accused of delivering an "anti-Pakistan" speech during his visit to Afghanistan. He did not provide any further details.

Jamal Malyar, a local leader of the PTM, said the charge against Wazir was "baseless."

The Human Rights Commission of Pakistan (HRCP) has said the authorities have made allegations of anti-state activities "an expedient label for human rights defenders, particularly those associated with the PTM."

The PTM has campaigned for civil rights for Pashtuns, the country's largest ethnic minority, since 2018.

The group has attracted tens of thousands of people to public rallies to denounce the powerful Pakistani Army's heavy-handed operations in the militancy-hit tribal regions and the military's alleged connection with Islamist militants.

The PTM has been calling for the removal of military checkpoints in tribal areas and an end to "enforced disappearances," in which suspects are detained by security forces without due process.

Pakistan's government rejects allegations that its security forces and intelligence agents are responsible for forced disappearances.

Since the movement was formed in January 2018, international rights groups say authorities have banned peaceful rallies organized by the PTM and some of its leading members have been arbitrarily detained and prevented from traveling within the country. Some members have also faced charges of sedition and cybercrimes.

Authorities in January arrested PTM leader Manzoor Pashteen on charges including sedition, hate speech, incitement against the state, and criminal conspiracy.

Pashteen was later released on bail.