The Hamas leader in Gaza urged militant groups on Thursday to stick with a de facto truce with Israel, announced after fighting last month, so as to give a Palestinian reconciliation deal with Fatah rivals a chance.

"I call for giving the coming government a chance by maintaining" the ceasefire deal, Ismail Haniyeh said in a speech, a day after Hamas and Palestinian President Mahmoud Abbas's Fatah movement signed a unity pact in Cairo.

"We do not fear threats. We do not fear the occupation," he added, referring to Israel.

"We always said that we seek and have sought to avoid a new war," Haniyeh said in a two-hour address.

Haniyeh's comments seemed the first concrete sign of progress for the unity deal brokered by Egypt for which security had been envisaged as a potential pitfall.

The agreement seeks to resolve a four-year split in the Palestinian national movement that had hindered the quest to achieve statehood in land captured by Israel in the 1967 war.

In reaching the deal, the sides had set aside the issue of bridging their policies toward Israel.

Unlike Abbas's group, which recognises Israel, Islamist Hamas refuses to recognise the Jewish state, hostility to which often results in cross-border violence.

Israeli strikes killed 19 Palestinians in a week-long bout of violence early last month after Hamas claimed responsibility for firing an anti-tank weapon at a school bus, wounding an Israeli teenager who later died of his injuries.

The United Nations helped the sides achieve a de facto truce which included a call to militants to halt rocket fire at Israel's southern towns.

Because of Hamas's potential role in the new Palestinian government, yet to be formed, Israel has denounced the unity deal as a blow to peace and has frozen the flow of vital tax revenue transfers to the West Bank.

Also in his speech, Haniyeh demanded that security forces under the control of Abbas's Fatah movement stop arresting Hamas sympathisers in the West Bank, territory where Fatah holds sway. Six have been arrested this week, a Hamas source said earlier.

"We still get calls from our brothers there that there are still arrests," Haniyeh said. "This does not serve the atmosphere we are seeking to establish.