Baton-wielding security officers in riot gear descended on the Migrant Accommodation Centre in Zhuravichi, Western Ukraine, where a group of about 60 Somalis and six Eritreans had been on hunger strike in protest against their illegal detention since 6 January.
Detainees at the centre told Amnesty International that security forces forced them to eat, and then filmed them doing so.
"The authorities must ensure there is no torture or other ill-treatment of these detainees, who should not be held in the first place," said John Dalhuisen Amnesty International's Deputy Director for Europe and Central Asia.
"These migrants and asylum-seekers are merely trying to escape human rights violations in their countries of origin and they are now being subjected to abuses in Europe."
Previously, detainees at the centre had reported that they were being beaten and ill-treated.
Some said they had been placed in an isolation unit without a bed for several days, and that they received anonymous emails and phone calls containing death threats and racist abuse.
The Somali nationals were rounded up by police in various parts of Ukraine around 23 December and the Eritreans were detained in November 2011.
The group includes about 20 children, some of whom are unaccompanied.
They have all been sentenced to up to a year of detention “for the purposes of deportation”. However, records show that no Somali or Eritrean nationals have ever been deported from Ukraine.
"As there is no prospect of deportation, there are no legal grounds for detaining these asylum-seekers and their detention is arbitrary and unlawful and they must be released," said John Dalhuisen.
"The Ukrainian authorities must stop the practice of detaining Somali and Eritrean nationals when there is no prospect of deporting them."
As a state party to the UN Refugee Convention, Ukraine cannot return anybody to a country where they would be at risk of grave human rights violations.