Israel escalated the war in Gaza by initiating a ground invasion with tanks, artillery and gunboats Friday.

The ground offensive could expand the operation, which Palestinian officials claim is killing large numbers of civilians in Gaza.

According to Reuters, Palestinian officials reported that 27 Palestinians, including a 70-year-old woman and a baby, were killed since Israeli troops invaded Gaza by foot. Gound forces were sent into Gaza late Thursday, which is a densely populated strip of land where 1.8 million Palestinians reside.

The Israeli Defense Forces said they killed 17 Palestinian gunmen, and 13 more surrendered and were apprehended for questioning after the ground assault began.

One Israeli soldier was killed in the operations.

So far, 150 targets, including 21 concealed rocket launchers and four tunnels, have been attacked by the Israeli military.

The ground invasion followed 10 days of fighting between Gaza and Israel with hundreds of rockets fired by Hamas into Israel and Israel responding with retaliatory air strikes. This week, Egypt tried to facilitate a cease-fire between the opposing sides, but it was violated when Hamas lobbed rockets into southern Israel.

Rockets from Gaza, with many intercepted by the IDF's sophisticated Iron Dome missile defense system, continued to be launched into Israel Friday. Israeli police said there were no casualties Friday.

Israeli forces targted the Al-Jawhara building Friday, which houses Hamas-affiliated media outlets. One journalist was wounded in the attack.

"We chose to start this operation after we exhausted other options and reached the conclusion that without it we could pay a much higher price," Israeli Prime Minister Benjamin Netanyahu told reporters in Tel Aviv. "The main goal is to restore quiet.

"My instructions ... to the Israeli army, with the approval of the security cabinet, is to prepare for the possibility of a widening, a significant widening of the ground operation."

Israel is using 18,000 military reservists in the escalated operation, in addition to the 30,000 that have already been recruited for the effort.

While the details of the offensive were not described, Israel said it is focusing on destroying tunnels that Palestinian militants use for raids across the border.

Israel prevented an infiltration by tunnel Thursday; the IDF stopped 13 gunmen from invading an Israeli farming community through a tunnel from Gaza.

Sami Abu Zuhri, a Hamas spokesman, told Reuters that Palestinians are not frightened by the ground invasion.

"Netanyahu is killing our children and will pay the price. The ground invasion doesn't frighten us, and the occupation army will sink in Gaza's mud," Zuhri said.

Hamas is demanding that Israel ease border restrictions that have led to unemployment and economic distress in Gaza.

Hamas said they are shelling Israeli tanks with mortars and setting off bombs near troops.

According to Palestinian officials, 260 Palestinians have been killed since fighting began on July 8.

Israel has had two casualties, when one soldier and one civilian were killed by rockets in two separate incidents. More than 100 rockets have been launched into southern Israeli towns, as well as in the capital city of Tel Aviv. Thousands of Israelis have been forced to run for shelter each day as rockets are launched into residential areas.

While the IDF is also hitting densely populated areas, the IDF sends out evacuation notices through dropping leaflets, sending automated phone messages and sending small warning rockets onto the tops of roofs to alert the residents to evacuate the premises.

Israeli officials have also said that many of the civilian casualties have resulted from Hamas embedding rocket launching sites in areas with civilian adults and children, thereby using civilians as "human shields." Israeli officials said that Hamas then blames the IDF for the casualties in order to garner international sympathy.

U.N. Secretary-General Ban Ki-Moon told Israel Friday to try to curb the high number of civilian casualties. German Chancellor Angela Merkel spoke out in support for Israel, saying they have no choice but to defend themselves against long-range Hamas rockets.

"Both sides must accept painful compromises but we stand by the side of Israel when it comes to self-defense," she said during a news conference in Berlin, according to Reuters.

The conflict began when three Israeli teens were kidnapped and killed in the West Bank and a Palestinian teenager was abducted and burned to death in an apparent revenge killing.

The conflict is the worst fighting in two years, and Israel has not had a large-scale ground invasion of Gaza since early 2009.