Israeli troops and aircraft attacked Islamic militants in the southern Gaza Strip Tuesday, killing three Hamas fighters, one Islamic Jihad militant and two civilians and wounding 26 people, Hamas and Palestinian medical officials said.

Hamas said one of its men died in a pre-dawn airstrike, east of the town of Khan Younis, and a second was killed along with his 70-year-old mother when ground troops fired at their house. The body of a third was found later in the day.

An Israeli army statement said that in an operation against "terror threats" from the southern Gaza Strip, forces fired at armed militants in four separate incidents and hit the targets on each occasion. A spokesman said aircraft carried out three attacks and ground forces shot a gunman posing a threat to soldiers.

Israeli Army Radio said troops were rounding up all local males above the age of 16 and interrogating them for information on militants. About 100 people were arrested by Israeli troops, the army and Hamas said.

Later, Israeli aircraft struck a group of Islamic Jihad militants as they exited a car in Khan Younis, killing one and seriously wounding another.

Hospital officials said overall 26 people were wounded, including 14 militants from the Islamic Jihad and five civilians.

Palestinian medical officials said a second civilian, Ibrahim al-Shami, 40, was shot dead by soldiers when he went out onto the roof of his house.

The army often carries out raids into Gaza to target militants and to thwart rocket fire toward Israeli towns.

The military said Palestinians fired a rocket from the northern Gaza Strip toward Israel on Tuesday morning. There were no reports of injuries or damage.

Also Tuesday, four Palestinians slipped into Israel through the heavily guarded Israel-Gaza border fence, the army said. It was the second such infiltration in two days. Four suspects were apprehended in southern Israel and questioned, the army said.

It was not immediately clear if the Palestinians were militants or civilians looking for work in Israel.