* Eight members of a family killed in Israeli raid
* Hamas says its gunmen engage Israeli troops at sea
By Nidal al-Mughrabi and Allyn Fisher-Ilan
GAZA/JERUSALEM, July 10 (Reuters) - Israel pressed on with a punishing aerial offensive in Gaza for a third day on Thursday, killing eight members of a family including five children in a predawn strike, Palestinian officials said, while militants fired rockets at Israeli cities.
The Israeli military had no immediate comment on the deadliest single bombing raid since the start of the offensive on Tuesday. The attack destroyed at least two homes in Khan Younis in southern Gaza, killing the eight people, the Palestinian Health Ministry said.
Sixty-one Palestinians have been killed in the violence, more than 50 of them civilians, Palestinian medical officials said.
Israel says its offensive is intended to halt rocket fire at its cities from the Gaza Strip. More than 200 rockets have been fired during the campaign, striking deep into the country's heartland, it said.
The rockets have caused no serious casualties, but the barrages have paralysed business in southern communities and sent hundreds of thousands of people scrambling for shelter as far north as the Israeli business hub of Tel Aviv and beyond. A rocket struck on the outskirts of Haifa to the north on Wednesday.
Hamas's armed wing said it fired six rockets at Israel early on Thursday. Confrontations were also reported at sea where Palestinian militants in Gaza said they fired mortars and rockets at Israeli gunboats shooting at the coastal territory.
Israeli media reported air raid sirens wailing in several southern cities. The Iron Dome missile defence system intercepted some of the rockets, while others slammed into the ground without causing any damage or casualties, they said.
Palestinians said Israel has targeted more than 70 homes in its offensive. The Israeli military said on Wednesday it had bombed 550 Hamas sites, including 60 rocket launchers and 11 homes of senior Hamas members. It described those dwellings as command centres.
SECURITY COUNCIL TO MEET
United Nations Secretary-General Ban Ki-moon is to address the U.N. Security Council on Thursday over the worst Israeli-Palestinian violence since an eight day war fought in 2012. He described the situation as "troubling and volatile."
Washington backed Israel's actions in Gaza, while the European Union and U.N. urged restraint on both sides.
Israel said Gaza militants fired more than 105 rockets on Wednesday - at least 82 struck inside the country, and an additional 21 were intercepted.
Some were aimed at Israel's Dimona nuclear plant, 80 km (50 miles) from Gaza, but were either shot down or landed in open country.
Dimona, desert site of a nuclear reactor and widely assumed to have a role in atomic weaponry, was targeted by locally made M-75 long-range rockets, militants said. The Israeli army said Iron Dome shot down one, and two others caused no damage.
Communities near coastal Tel Aviv and in the south, closer to Gaza, were also targeted. In the longest-range attack since the offensive began, a rocket hit near Zichron Yaakov, a town 115 km (70 miles) north of Gaza, on Wednesday.
Israel said it attacked 326 targets in Gaza on Wednesday, including concealed rocket launchers, tunnels suspected of being intended for armed cross-border infiltrations, training bases, and weapons storage and production facilities.
In an attack after darkness fell, Israel targeted a car marked as a media vehicle of a Gaza website that had the letters "TV" on it. It killed the driver, medical officials said.
Four people were killed in the bombing of a cafe in Khan Younis, and a 37-year-old man was killed in central Gaza, hospital officials said.
The Israeli-Palestinian violence began building up three weeks ago after three Jewish students were abducted in the occupied West Bank. They were killed and their bodies were found last week. Then a Palestinian teenager was kidnapped and killed in Jerusalem.
Cairo brokered a truce after an eight-day war between Israel and Gaza militants two years ago, but the current military government's hostility towards Islamists in general and Hamas in particular, which it accuses of aiding fellow militants in Egypt's Sinai peninsula, could make any Egyptian mediation role difficult now. Hamas denies those allegations.
Israeli leaders, who have popular support for the Gaza offensive, have warned the campaign may be lengthy and expand into a ground invasion of one of the world's most densely populated territories.
Prime Minister Benjamin Netanyahu's security cabinet has approved the potential mobilisation of up to 40,000 reserve troops.
Palestinian President Mahmoud Abbas, who is based in the Israeli-occupied West Bank, denounced the offensive on Wednesday.
"This war is not against Hamas or any faction but is against the Palestinian people," said the Western-backed Abbas, who entered a power-sharing arrangement with Hamas in April after years of feuding.
Hamas's attacks against Israel are seen as an effort to provide a popularity boost for the Islamists whose rift with Egypt's military-backed government has deepened economic hardship for the nearly 2 million Palestinians living in the enclave.
Under President Abdel Fattah al-Sisi, Cairo has secured closures on the Gaza border, adding to economic pressures on Hamas from a long-running Israeli blockade.
Israel has blamed Hamas for killing the three Jewish seminary students who disappeared while hitchhiking in the West Bank on June 12. Hamas has neither confirmed nor denied a role. (Writing by Allyn Fisher-Ilan; Editing by Mohammad Zargham and Ken Wills)