Asylum seekers at a Darwin detention centre are reportedly blockading a compound to stop several Iranian families being returned to Nauru.
The stand-off at Wickham Point detention centre began at 2pm on Wednesday.
The Refugee Action Coalition said about 70 asylum seekers were involved.
It said a woman earmarked for removal was pregnant.
About 20 detainees have committed self harm, the ABC reports.
The immigration department has rejected claims of a riot and declined to confirm the self harm incidents.
"A disturbance occurred involving detainees resulted in minor property damage," a department spokesman said.
Police are attending the centre.
