Hamas announced Sunday that all its members currently sitting in Israeli prisons will launch a hunger strike on Monday, after Israel transferred senior Hamas officials to solitary confinement.

A Hamas spokesman said Sunday that the purpose of the hunger strike was to demand the release of Yihyeh Sanwar, who is considered the most senior Hamas official in prison, and his brother Mohammad, who was among those responsible for the abduction of Israeli soldier Gilad Shalit. According to the Hamas spokesman, Sanwar suffers from serious health problems.

According to Hamas, at least six more senior Hamas officials were recently transferred to solitary confinement.

Israel Prison Service officials refused to confirm or refute the new information.

Netanyahu announced last week that Israel plans on toughening the conditions of Palestinian security prisoners, saying that the "celebration is over for terrorists."

Meanwhile on Sunday, Hamas rejected Prime Minister Benjamin Netanyahu's claim that Israel had accepted a German-mediated proposal for a prisoners swap deal involving abducted IDF soldier Gilad Shalit, calling Netanyahu's comments "lies" and saying he is "fully responsible" for the stalemate in negotiations for a prisoner swap deal.