Israel's military says it has struck Hamas targets in the Gaza Strip in response to rocket fire toward Israel.

The military says sirens wailed in southern Israel early Saturday warning of an incoming rocket. One landed in an open field, causing no injuries. The military says it retaliated against the territory's Hamas rulers.

Gaza militants have fired mortar rounds at Israel over the past three days, prompting Israeli retaliation. Palestinian attacks intensified after Israel uncovered an attack tunnel Thursday beneath the border.

Hamas used tunnels to attack Israel during the 50-day Gaza war in 2014 and fired thousands of rockets. The recent exchanges of fire are among the most serious since the war ended.