Shells slammed into densely populated neighborhoods. Families wept over bloodied corpses and medical workers rushed to keep up with the wounded Friday as Israeli forces hunted rocket launchers and tunnels that Palestinian militants use to strike Israel.

Troops backed by tanks and artillery pressed deeper into the coastal enclave in a ground offensive launched Thursday after 10 days of aerial bombardments failed to halt the rocket fire raining down on Israel's cities and towns from Gaza, which has been controlled by Hamas since 2007.

Israel has launched previous campaigns, including a major ground operation early in 2009. Each time, Hamas has quickly rebuilt its arsenal of rockets, which have grown more powerful and can now penetrate deep into Israeli territory.

Hard-liners in Israel have been calling for an all-out assault to drive Hamas from power. This incursion appeared more limited in scope, targeting a network of tunnels along the enclave's northern, eastern and southern frontiers that militants use to smuggle weapons and fighters into Israel.

But Prime Minister Benjamin Netanyahu told reporters he had instructed the military to prepare for the possibility of a “considerable expansion of the ground operation.”

“We chose to embark on this operation after exhausting the other options and with the understanding that without the operation, we could pay a much higher price,” Netanyahu said as he headed into a meeting of his Security Cabinet.

More than 1,600 rockets have been fired at Israel since July 8, according to Israeli authorities. The country's Iron Dome antimissile system, built with U.S. assistance, has helped keep Israeli casualties to a minimum. One Israeli was killed by shelling from Gaza, and an Israeli soldier was killed during the ground operation. The cause of the military death was under investigation, but Israeli news reports said that friendly fire was suspected.

Nearly 300 Palestinians have been killed, most of them civilians, by Israeli airstrikes and ground attacks, according to Gaza medical officials quoted by the Maan news agency. More than 60 of them died since the ground operation began.

Heavy fighting was reported in the northern Gaza cities of Beit Hanoun and Beit Lahiya, as well as around Khan Yunis and Rafah to the south.

Among the Palestinians killed Friday were three siblings ages 13 to 15 who died when their house in Beit Lahiya was shelled. A separate attack killed at least eight members of an extended family in Khan Yunis, according to Palestinian accounts.

Loud explosions resonated throughout the day, sending families living in Gaza's frontier areas fleeing toward the interior on foot and in donkey carts.

Others, however, were afraid to leave their homes.

“Where to go?” lamented Sharhabeel Mahmoum, a 37-year-old pharmacist and father of four reached by telephone in Beit Lahiya. “As long as Israeli planes are in the air, there is no safe place.”

Ambulances cruised the streets searching for victims. A distraught man arrived at the Shifa hospital in Gaza City with two young children, their faces peppered with shrapnel wounds. In the hospital morgue, relatives grieved over the body of a woman covered with a soiled sheet.

Constant bombardment has made life miserable in the impoverished enclave, knocking out already patchy power and water service and keeping families pinned down in their homes.

Bodour Kwaik, a 24-year-old aid worker, lost two family members in an Israeli airstrike early in the campaign. “I couldn't even say good-bye,” she said from her Gaza City apartment. “I couldn't go to the funeral because it was too risky.”

Israeli military officials said the complex network of tunnels through the Gaza Strip remains a potent threat, linking weapons caches and rocket launch-sites with homes and mosques used by militants to strike at Israel.

“There appears to be some misunderstanding of how severe the tunnel threat really is,” said retired Maj. Gen. Gadi Shamni, a former commander of the Israel Defense Forces' Gaza Division. “A successful attack through such a tunnel … can turn everything around.”

Before the ground offensive began Thursday, Israeli officials said they intercepted 13 heavily armed fighters at the mouth of a tunnel in Israel. An airstrike is believed to have killed three of them, but the rest escaped, said Lt. Col. Peter Lerner, an Israeli military spokesman.

A similar tunnel was used to capture an Israeli soldier, Gilad Shalit, in 2006. He was held for five years, until Hamas agreed to release him in exchange for more than 1,000 Palestinian prisoners .