Middle East crisis: Israel releases 'Gaza tunnel footage'

Israel sent ground troops into Gaza on Thursday, saying the ground operation is necessary to target Hamas' network of tunnels.

It has stated the tunnels pose a threat of terrorist attacks against the Israeli population.

Israel said it had killed more than 170 militants since Thursday night, when it launched the offensive.

Air strikes are also continuing, with the Palestinian death toll reportedly nearing 600, the majority of them civilians.

The BBC looks at Israel Defense Forces footage from the operation.