JERUSALEM (Reuters) - Israeli Prime Minister Benjamin Netanyahu on Thursday instructed the military to begin a ground offensive in Gaza, an official statement from his office said.

Reuters witnesses and Gaza residents reported heavy artillery and naval shelling and helicopter fire along the Gaza border.

"The prime minister and defence minister have instructed the IDF to begin a ground operation tonight in order to hit the terror tunnels from Gaza into Israel," the statement said.

Israel and Palestinian militants in the densely populated enclave have been fighting a cross border war for the ten days.

The Israeli military says Gaza militants have fired more than 1,300 rockets into Israel, and Palestinian health officials say 233 Palestinians have been killed in Israeli air and naval strikes. One Israeli civilian has been killed by fire from Gaza.

A statement from the Israeli military said the operation will include "infantry, armoured corps, engineer corps, artillery and intelligence combined with aerial and naval support."

Before dawn on Thursday, about a dozen Palestinian fighters tunnelled under the border, emerging near an Israeli community. At least one was killed when Israeli aircraft bombed the group, the military said.

(Writing by Maayan Lubell; Editing by Louise Ireland)