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GAZA, Jan 4 (Reuters) - Israeli air strikes killed two Palestinian militants and six civilians in the Gaza Strip on Sunday, medical officials and a militant group said.

The Islamic Jihad said two of its fighters were killed when missiles fired by an Israeli aircraft slammed into their car in the northern Gaza Strip. Three civilian passers-by were also killed in the attack, medical workers said.

Shortly after, an Israeli air strike targeted a car north of Gaza City, killing three passengers whom medical workers said were volunteers with Palestinian emergency services.

The attacks brought to 42 Sunday's Palestinian death toll. The Israeli army pushed on with its offensive against militants in the enclave, forging ahead with a ground incursion and maintaining an air campaign that started eight days ago.

Some 512 Palestinians have been killed so far in the operation, which Israel says is aimed at stamping out rocket attacks from Gaza and weakening the enclave's Hamas rulers.

Four Israelis have been killed in rocket attacks since the start of the assault. An Israeli soldier was also killed on Sunday. (Reporting by Nidal al-Mughrabi, Writing by Joseph Nasr, Editing by Richard Meares)

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