The Israeli military began a ground offensive in the Gaza Strip on Thursday night.
The military issued a statement at 10:40 PM announcing the launch of the operation. It says the new phase follows 10 days of Hamas attacks on Israel and repeated rejections of offers to de-escalate the situation.
The statement says the goal is to target Hamas's tunnels that cross under the Israel-Gaza border, enabling terrorists to infiltrate Israel and carry out attacks.
This is the first Israeli ground operation in Gaza since 2009.
Details of the operation are not known.
An NHK reporter in Gaza says fierce attacks appear to be underway in eastern Gaza, and big explosions can be heard in western Gaza.
Since Sunday, Israeli forces have been warning residents near the border between Gaza and Israel to evacuate.
Egypt had brokered a ceasefire, but no agreement has been reached as of Thursday.
231 people, including many civilians, have been killed in the attacks on Gaza. More than 1,700 people have been wounded.
Jul. 17, 2014 - Updated 22:24 UTC