JERUSALEM/GAZA -- Mortars launched from the Gaza Strip on Monday afternoon hit a bus and a residential home in southern Israel, seriously injuring a 19-year-old, Israeli officials said.

The attack came just a day after Israeli airstrikes in Gaza killed seven people.

Code Red sirens were sounded in multiple communities in the vicinity of the Gaza Strip, while the military's Home Front Command instructed residents to take shelter in protected areas.

A spokesperson for the regional council of Eshkol said in a statement that "heavy barrages" were fired toward the region and explosions were heard.

The David Magen Adom emergency service said a 19-year-old young man was "in a serious condition with multi-system injuries."

Mortars from Gaza also hit a home in the western city of Sderot, causing no injuries, according to the medical services.

The southern cities of Netivot and Ofakim were also confirmed to be hit.

A short statement by the joint operation room of militant groups, including Hamas, confirmed the attacks.

"The Palestinian armed resistance on Monday evening fired scores of rockets from the Gaza Strip on the settlements of the enemy," the statement said.

In response, Israeli air force bombed several sites in Gaza following the attacks, Palestinians reported.

The recent escalation started on Sunday night, when Hamas uncovered Israeli forces during a special mission inside the Gaza Strip and killed an Israeli officer, according to Hamas.

The incident prompted Israel to launch massive airstrikes in retaliation, killing seven Palestinians, Hamas and Gaza health officials said.

Israel's military provided few details on the incident.

Gaza militants later fired rockets toward southern Israel with 17 launches identified by the Israeli military, three of which were intercepted, an Israeli military spokesperson said.

Tensions in the region were still high on Monday morning, with schools cancelled for students in southern Israel for security concerns.

Israeli Prime Minister Benjamin Netanyahu cut short his trip to Paris and returned overnight, according to a statement from his office.

At a news conference in Paris on Sunday, Netanyahu defended his decision to move toward an unofficial cease-fire with Hamas.

He also warned that if calm along the border will not be kept, Israel "will act with maximum power."

The sudden burst of violence potentially shattered hopes for a long-term agreement between Israel and Hamas, as Egyptian and the UN officials have been working to broker a cease-fire deal in exchange for Israeli easing its 12-year crippling blockade on Gaza.