Clashes broke out on Israel’s border with Gaza late on Thursday as the Israeli army was conducting what it said was a defensive operation against a recently discovered concrete-lined, mile-long tunnel from Gaza into Israel.

The Israeli military said militants planned to use the tunnel to attack or kidnap Israelis.

In 2006, Hamas-allied militants sneaked into Israel through one such tunnel, killed two Israeli soldiers and kidnapped a third, holding him hostage in Gaza for five years.

At least three Palestinian militants were killed Thursday’s violence, the enclaves Hamas rulers said.

Hamas said the Israeli tanks had entered the Gaza side of the border. Clashes erupted as militants fired mortar shells at the tanks. Hamas added that an Israeli helicopter fired a rocket in the area.

An Israeli military spokeswoman said forces were carrying out “a pinpoint action” in the area of the tunnel in the Gaza Strip but did not have further details.

The Israeli army had no immediate comment on its own casualties, however Israeli television showed injured Israeli soldiers in hospital.