(Updates casualty toll)

By Nidal al-Mughrabi

GAZA, Dec 20 (Reuters) - Israeli tanks and troops backed by helicopter gunships raided the central Gaza Strip on Thursday, killing at least seven Palestinian gunmen, militant sources and hospital officials said.

They said Israeli forces operating east of Maghazi refugee camp, a few hundred metres (yards) in from Gaza's boundary fence, exchanged fire with gunmen. Four of the dead were Islamic Jihad militants and three belonged Hamas, the groups said.

Several other Palestinians, including a 7-year-old boy and a Reuters Television sound operator, Nihad Odehtallah, were wounded.

An Israeli military spokesman described the raid as "a routine operation against terrorist threats" and said troops shot at least seven armed Palestinians. One Israeli soldier was severely wounded in the clashes, the army said.

Odehtallah was taken to hospital with a bullet wound to his left thigh and was sent home after treatment.

"The bullet went in and out. There was no fracture or vascular injury," said a doctor at the facility.

Odehtallah said he and other journalists were near an ambulance when gunfire erupted.

"I didn't see who shot me. I couldn't identify who was firing," he said.

Asked about the incident, a military spokeswoman said: "We received the report of the soundman who was injured in the area where Israeli forces and terror groups exchanged fire. If there had been a shooting, at this stage we are unable to determine its source. We emphasise that it happened in a battle zone."

Israel stepped up ground and air operations this week against Islamic Jihad, which has spearheaded cross-border rocket attacks from Gaza.

Three rockets were launched against the Israeli border town of Sderot on Thursday, one of them landing 40 metres (yards) from a school, police said. Ten pupils were treated for shock.

Hamas said it fired 21 mortar bombs at Israeli border posts. There were no reports of casualties from those attacks. (Additional reporting by Ari Rabinovitch in Jerusalem, Writing by Dan Williams and Jeffrey Heller in Jerusalem, Editing by Michael Winfrey)

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