Hamas Warns of 'Heavy Price' for Israel

Deadly clashes broke out after Israeli tanks drove into Gaza and launched a ground operation that escalates the conflict with Hamas.

The incursion Thursday night follows 10 days of Israeli bombardment of Gaza that has killed more than 250 people. Israel launched the aerial offensive last week, saying it aimed to halt the firing of Hamas rockets from Gaza into Israel.

Israeli Prime Minister Benjamin Netanyahu and Defense Minister Moshe Yaalon ordered the ground operation to destroy tunnels dug from Gaza into Israeli territory, according to a statement.

Thirteen Hamas militants used a tunnel earlier Thursday to launch an attempted attack in Sufa, near an Israeli kibbutz, but were stopped by Israeli soldiers, the Israel Defense Forces said.

The IDF said it had sent a "large" force into Gaza that includes infantry, tanks, artillery, combat engineers and intelligence units, with aerial and naval support.

CNN's Wolf Blitzer asked Mark Regev, Netanyahu's spokesman, whether Israel planned to occupy Gaza for a long time.

Regev didn't answer directly, but said Israel's goals are to "diminish" the Hamas military force and to show that it cannot attack Israel with impunity.

You can follow all the developments at CNN.com.