Defense Minister Ehud Barak on Monday called for Gaza Strip border crossings to close starting on Tuesday, hours after Palestinian militants fired two mortar shells into Israel, which struck an open space between the Karni crossing and Nahal Oz causing neither casualties nor property damage.

Since the cease-fire between Israel and Hamas went into effect in the Gaza Strip June 19, militants have fired several Qassam rockets into Israel, including one last week that fell in the western Negev region.

Israel closed its border crossings with Gaza in the wake of the rocket fire, but reopened them on Sunday to allow goods into the Strip and Gazans in need of medical assistance out of the coastal territory.

A farmer operating a tractor near the western Negev Kibbutz Nahal Oz on Sunday said a Palestinian sniper in the bordering Gaza Strip opened fire on him. Several hours later, however, the military admitted there was no sniper attack, saying damage to the tractor might have been caused by a stone.

The farmer sustained no wounds.

A police sapper from the nearby city of Sderot arrived at the scene but could not determine whether a shooting had taken place because he could not locate a bullet.

The incident occurred hours after Israel reopened its border crossings with Gaza, a measure stipulated by the truce agreement between Israel and the Palestinian militant group Hamas.

Israel pledged to open the crossings, but it has repeatedly closed the passages in response to Palestinian violations of the truce in the form of Qassam rockets and mortar shells fired into Israeli communities.