A total of 13 Israeli hostages are to be freed "tonight" for 39 Palestinian prisoners, in a delayed second exchange agreed as part of a temporary truce in Gaza, mediator Qatar said Saturday.

Seven foreigners held in Gaza will also be released, it added.

"After a delay, obstacles to release of prisoners were overcome through Qatari-Egyptian contacts with both sides, and 39 Palestinian civilians will be released tonight, while 13 Israeli hostages will leave Gaza in addition to 7 foreigners," foreign ministry spokesman Majed Al Ansari wrote on X, formerly Twitter.

Earlier, Hamas said it was delaying the release of a second group of Israeli hostages in exchange for Palestinian prisoners until Israel complies with a truce agreement.

In a second post, Ansari said the Israelis to be released from Gaza consisted of eight children and five women.

Those to be released from Israeli prisons comprised 33 children and six women, the spokesman said.

On the first day of a four-day humanitarian truce in Gaza, facilitated by Qatar with help from Egypt and the United States, 13 Israeli hostages were freed by Hamas Friday in exchange for 39 Palestinian prisoners held in Israeli jails. Hamas also freed 10 Thais and one Filipino.

A total of 50 Israeli hostages are to be freed by Hamas in staggered releases over the four-day truce in exchange for 150 Palestinian prisoners.

It is by far the largest release since Hamas gunmen stormed across Gaza's militarised border on October 7 and staged the deadliest attack in Israel's history.

Israel says the attack killed 1,200 people, mostly civilians, and saw around 240 more taken hostage.

In response, Israel launched a relentless bombing campaign in Gaza, which its Hamas government says has killed nearly 15,000 people, thousands of them children.