Israeli troops on Saturday killed at least three Hamas militants who were en route to carrying out an attack, throwing an already shaky truce along the Gaza-Israel border further into question.

The border clash came just a day after moderate Palestinian President Mahmoud Abbas held rare talks in Cairo with Hamas' supreme leader in exile, Khaled Mashaal, to find ways of rescuing the cease-fire.

The attempted attack was seen as a snub of both Abbas and Egyptian mediators. According to an Israeli media report, Egypt has threatened to cut ties with Hamas if the group does not respect the cease-fire.

It was not clear whether Hamas' military wing acted with the backing of the political leadership. There has been growing dissatisfaction among Hamas' hard-liners with the coalition government formed in March between Hamas and Abbas' pragmatic Fatah movement.

In Saturday's incident, four armed Palestinians tried to plant a bomb near the Gaza-Israel border and were killed by Israeli troops, the Israeli military said. Palestinian militants have attempted to plant more than 50 bombs near the border since the cease-fire took effect, the army said.

Palestinian medics said they found three bodies in the area and that a fourth person was seriously wounded. Hamas said the three dead were members of its military wing.

Saturday's incident marked the second time in four days that Hamas breached the cease-fire reached in November. Earlier this week, Hamas fired a barrage of rockets toward Israel, causing no injuries, after Israeli forces killed nine Palestinians in fighting.

"The truce cannot be for free. There is a possibility to consider a temporary truce, on the condition that is mutual. Otherwise there will be no free truce," Abu Obeida, a spokesman of the Hamas military wing, told a local Palestinian radio station.

Hamas has sent mixed messages about the truce in recent days.

While the military wing said it considered the truce to have ended, citing Israeli violations, political leaders said the future of the cease-fire depended on Israeli actions.

Ayman Taha, a Hamas government spokesman, said Saturday that the group has the right to target Israel. "The problem is not with the resistance, it is with the occupation," he said.

Another Palestinian militant group, the Popular Resistance Committees, said it fired three rockets toward Israel in response to the deaths.

An Abbas aide, Saeb Erekat, said the truce was a key item on the Abbas-Mashaal agenda on Friday.

"The main theme in the meeting was how to sustain the cease-fire and Abu Mazen (Abbas) reiterated that the cease-fire is a paramount Palestinian interest, and that this should stop," Erekat said. He said Egyptian mediators also carried a message to Israel, asking for a halt in army operations.

Also Saturday, another militant, was found dead close to the Gaza-Israel border, his body torn apart by an explosive device, medics said. Shadi Abu Zaher was planting explosives along the Gaza-Israel border when he was killed by a tank shell, the Popular Front for the Liberation of Palestine militant group said in a statement sent to local radio.

The army said it was not involved in the incident in any way.