An explosive device was activated Friday morning against IDF troops operating along the security fence in the southern Gaza Strip. No injuries were reported in the incident.

Israeli forces responded with tank fire at suspected lookout posts near Khan Younis on the Palestinian side, the IDF spokesman’s office reported.

Palestinian media reported six injured by the IDF retaliatory fire, including one in critical condition.

The attack followed an incident Sunday in which a lone terrorist from the Gaza Strip, armed with a grenade, managed to cross the border into Israel unchallenged.

The inquiry into the incident ended on Thursday with two officers being dismissed from their posts and several other soldiers being disciplined.

The inquiry, led by Southern Region Commander Major General Shlomo Turgeman, found that although forces were alerted when the terrorist climbed over the Gaza border fence early Sunday, an IDF patrol was scrambled to the wrong location and failed to find him.

The deputy company commander of an infantry unit and a female operations officer in the command center were both dismissed from their posts.

In addition, a disciplinary note was entered into the record of the battalion commander of the infantry unit involved, and the company commander was reprimanded as well as having his future promotions delayed. An unspecified number of non-commissioned soldiers who manned the command center on the night of the breach were to receive disciplinary hearings, as were a scout and a surveillance soldier.

The incident occurred in the Eshkol region, adjacent to the southern Gaza Strip. After scaling the fence in the middle of the night a Palestinian man, armed with a hand grenade, walked five kilometers through Israeli territory before finally being safely apprehended by a civilian security officer near Moshav Yated.

IDF officials believe the man acted alone and was not sent by a terrorist organization.

Stuart Winer contributed to this report.