Qatar said Tuesday it was too soon to start brokering talks on a potential prisoner exchange between Israel and Hamas after the Islamists seized around 150 hostages in a shock weekend attack.

Israel has been left reeling by the coordinated ground, air and sea assault from Gaza which saw hundreds of militants storm the border on Saturday, before mounting a bloody rampage that killed more than 900 people.

Qatari foreign ministry spokesman Majed bin Mohammed Al-Ansari said it was "too early" for mediation when asked about the prospects for a potential prisoner exchange.

"At this moment, it is a very difficult point to say that any party can start with mediation. I think we need to see developments on the ground," he told reporters.

Concerns for the safety of those abducted to Gaza took on added urgency on Monday as Hamas threatened to start executing its prisoners if Israel carried out air strikes on Gaza without prior warning.

Israel has launched a ferocious retaliatory bombardment of what it says are Hamas targets in Gaza. Officials say at least 687 people have been killed.

On Monday, an informed source told AFP Qatar was spearheading efforts to negotiate an exchange of prisoners with talks making "some headway".

Late on Monday, Qatari Foreign Minister Sheikh Mohammed bin Abdulrahman Al-Thani held a call with his Iranian counterpart Hossein Amir-Abdollahian, whose government is a supporter of Hamas.

"We have discussed with all those we have contacted the need to contain this escalation within the current parameters and for it not to become a regional confrontation with other players," the ministry spokesman said, expressing particular concern over the situation in southern Lebanon.

Qatar, which has hosted a Hamas political office for more than a decade, has provided millions of dollars in financial aid to Gaza.

Late last month, Qatar and Egypt brokered a deal between Hamas and Israel which saw the reopening of border crossings between Gaza and Israel.