Wounded Fatah supporters were treated in Israel at the weekend.
Israeli security agents are putting pressure on some Palestinian medical patients to become informants, according to a human rights group.
Physicians for Human Rights says it has documented about 30 cases of people from Gaza being denied treatment for not providing information.
The Tel Aviv-based group says this breaches international law.
An Israeli official dismissed the claims, saying patients were only questioned as a security measure.
The report says that Palestinian patients have "become an accessible and important target for the GSS [General Security Services] for the purposes of recruiting and gathering information".
The group cites cases in which patients were summoned for questioning and others where patients did not come to a crossing for fear of being arrested.
'Need to question'
The Gaza Strip has been under an Israeli blockade since the militant group Hamas seized control in June 2007.
Although most people cannot leave the territory, medical cases are being considered for permission to get out.
Physicians for Human Rights says doctors, not security forces, should decide who can be granted that permission.
Israeli defence ministry spokesman Shlomo Dror told AFP news agency that everybody who entered Israel had to be questioned about the reason for their visit, "especially if they are in a terror organisation".
"These people are not going to assist us, because the moment they come back to Gaza they are already suspected of being collaborators," he added.
"We do not waste time and effort on people who cannot help us."
On Saturday, Israel granted temporary refuge to more than 180 supporters of Palestinian President Mahmoud Abbas following fierce fighting in Gaza with their Hamas rivals.
Many of them were wounded and received treatment in an Israeli hospitals.