An 84-year-old Israeli hostage, Elma Avraham, was released by Palestinian Hamas militants on Sunday and rushed to a hospital intensive care unit with her life in danger, the hospital director said.

Avraham "is in critical condition. She's treated in our emergency department after serious neglect for the last several weeks while being held by Hamas", said Shlomi Codish, head of the Soroka Medical Centre in southern Israel.

Avraham, an artist, was kidnapped along with others on October 7 when Hamas fighters launched an unprecedented bloody attack on Israel.

The Israeli army estimates that 240 hostages were seized and taken back to the Gaza Strip.

According to Avraham's son Uri Rawitz, who spoke to her on Sunday, the octogenarian had not managed to lock the door to the safe room in her house when the attack happened.

Rawitz later received a photograph of his mother being taken away on a motorbike by armed fighters with another hostage.

Avraham was among a group of 17 hostages, most of them Israelis, who were freed on Sunday after seven weeks in captivity.

Israel freed 39 Palestinian prisoners, in the third such exchange of a four-day truce which began on Friday.

"It is horrific that we now need to care for elderly patients held in underground tunnel for seven weeks with total medical neglect and disregard to their care," said Codish.