An Israel Air Force strike in the southern Gaza Strip killed two Palestinians Tuesday, dealing a new blow to efforts to restore a fraying cease-fire.

The army said it attacked a group of militants who had fired mortar shells at Israel Defense Forces troops from the area.

But Palestinian medical officials said the dead were civilians - a pair of teenage brothers who were struck outside their house. The identities of four people wounded were not immediately known.

The ruling Hamas militant group said its fighters had used the area to fire shells at Israeli targets earlier Tuesday.

Israel and Hamas have been observing a truce since June. But the cease-fire has begun to unravel over the past month, with Palestinian militants firing rockets and mortar shells at Israel and the IDF responding with attacks on militant targets.

Both sides say they still hope to restore the calm.

IDF soldiers, meanwhile, shot and killed a Palestinian militant on Tuesday during a raid in the West Bank city of Nablus on Monday, the IDF said.

On Sunday, a Qassam rocket fired by militants in the Gaza Strip struck a square in the center of the southern town of Sderot. No injuries or damage were reported in the attack.

Over the weekend, eight Israel Defense Forces soldiers were wounded, two of them seriously, when a barrage of mortar shells fired from Gaza hit an army base near the kibbutz Nahal Oz.

Among the wounded was Noam Nakash, whose leg was amputated as a result of the wounds incurred during the attack. Six of the wounded were still hospitalized on Sunday, two in serious condition, one moderately hurt and three with minor wounds.