Amnesty International criticized Japan on Tuesday for violating international standards by forcefully deporting detained foreigners against their will, including some undergoing medical treatment or preparing to appeal their refugee status.

The human rights group said that since the beginning of the year, at least four Iranian detainees at the Eastern Japan Immigration Detention Center in Ibaraki Prefecture have been forcefully deported without their consent or prior notice. They were not permitted to contact their families in Japan, lawyers or supporters before being deported.

Some families said the deportees were detained by local authorities after being sent back to Iran, according to Amnesty.

Amnesty said in a statement that Japan, which acceded to the U.N. convention against torture in 1999, must ensure that foreigners who might face torture upon returning to their countries should not be deported.

It also reiterated concern over a joint declaration issued in October by the immigration authorities, the Tokyo Metropolitan Government and the Tokyo Metropolitan Police Department to swiftly deport illegal foreigners, saying such actions will result in inhumane treatment.