Australia's Immigration Department said on Saturday that 13 detainees had inflicted "self-harm" but said no deaths had occurred.
It did not give details of the incident at the Villawood detention camp in Sydney.
"Twelve men and one woman cut themselves and another woman suffered an apparent heart attack when she saw what was occurring," Ian Rintoul, spokesman of Refugee Action Coalition, said.
He said other Villawood detainees also told him the group was made of mostly Chinese adults.
Some of the detainees were facing deportation, while one of the women was awaiting a ruling on her application for political asylum, Rintoul said.
No further comment
"A group of people have self-harmed and that's all we are saying at this time," said an Immigration Department spokesman.
Uniting Church refugee advocate Frances Milne said she was puzzled by the attempted suicides. "The government just yesterday indicated it maybe softening its position on detainees."
Prime Minister John Howard said on Friday his government was looking at ways to speed up rulings on immigration applications.
"Twelve men and one woman cut themselves and another woman suffered an apparent heart attack when she saw what was occurring"
spokesman of Refugee Action Coalition
Under changes proposed by Howard, refugee applications will be processed within six months.
Australia has some of the toughest anti-immigration laws.
Its immigration detention camps, which have been condemned by international human-rights groups, have long witnessed hunger strikes, riots, and suicide attempts by inmates protesting the government's lengthy hearing process, which can take years.
Refugee advocates insist at least some of the Chinese detainees held in Australia were political dissidents or members of the Falun Gong spiritual movement.
The Falun Gong mixes meditation with Buddhism, Chinese mysticism and exercises. The Chinese government denounces it as an evil cult.
Australia is also investigating claims by a Chinese diplomat seeking asylum that Beijing operates a network of some 1000 spies and informants in Australia.
Chen Yonglin, the political affairs consul at Sydney's Chinese consulate, has been in hiding in Australia with his family for fear of being kidnapped and whisked back to China after claiming his role at the consulate was to spy on and persecute Falun Gong practitioners. China has dismissed the claims as unfounded.