The leader of the Palestinian militant group Hamas says he is unsure of whether a long-term truce with Israel over the Gaza Strip can be announced on Sunday, as previously planned.

Exiled Hamas leader Khaled Mashaal told reporters on Friday that there have been some complications and that Egyptian negotiators may need more time to announce a cease-fire.

The uncertainty was compounded by a fresh bout of violence in Gaza on Friday.

An Israeli airstrike killed one militant and injured another near the Gaza town of Khan Younis. Israel's military says the men, who were members of the Popular Resistance Committees militant group, were planning to carry out an attack inside Israel.  

Israeli aircraft also bombed several smuggling tunnels. The airstrikes followed Palestinian rocket attacks on southern Israel from the Gaza, which caused no damage or injuries.

In the West Bank, a 14-year-old Palestinian was killed during what the Israeli military said was a clash between Israeli forces and a group of Palestinians.

In another development, two Palestinian ministers, Justice Minister Ali Kashan and Foreign Minister Riyad al-Maliki, presented their case to the International Criminal Court to open a war crimes investigation of Israel's recent offensive in Gaza.

The Palestinian officials said they presented documents showing they have the legal standing, as officials of a Palestinian state, to request an investigation.

An ICC prosecutor must decide whether the court has the jurisdiction to hear the case before he can determine whether war crimes were committed in Gaza.

Israel does not recognize the court's authority.

Both Israel and Hamas called separate cease-fires on January 18, after Israel's three-week offensive on Gaza, which killed more than 1,300 Palestinians.  Thirteen Israelis also were killed in the conflict.

In other news, Palestinian authorities are searching for 13 Palestinian prisoners who escaped from a prison in the West Bank city of Jericho on Friday.  Officials say at least four of the inmates are wanted for political or security-related offenses.

Some information for this report was provided by AFP, AP.