Relatives of two Palestinian teens killed by an Israeli airstrike mourn during their funeral Sunday.
Jerusalem CNN  — 

Two Palestinians in Gaza were killed Saturday night in Israeli airstrikes after four Israeli soldiers were wounded by an explosive device along the Gaza border.

The hostilities mark some of the most serious clashes since the end of the 2014 Gaza war.

Salem Sabah and Abdallah Abu Sheikha, both 17 years old, were killed Saturday night when the Israeli military carried out a series of air and tank strikes across Gaza, according to the Palestinian Ministry of Health and the Palestinian news agency WAFA.

The strikes hit 18 Hamas targets, including what the Israeli military called an “offensive terror tunnel” in Zaytun in southern Gaza, Israel Defense Forces (IDF) said.

The strikes were carried out in response to an explosive device that detonated on the Gaza border earlier Saturday, injuring 4 soldiers. Two of the soldiers were severely injured, the Israeli military said. It was not immediately clear who was responsible for that bombing.

The four soldiers were a combination of infantry and explosive ordinance disposal (EOD) forces, sent on foot to investigate a Palestinian flag placed along the border, Israel Defence Forces spokesman Lt. Col. Jonathan Conricus told CNN.

Conricus said the flag was placed along the border during Friday demonstrations, which have been common along the fence separating Gaza from Israel.

“The Hamas terror organization is accountable for this incident and its consequences, as well as everything happening in and from the Gaza Strip, above and below ground,” the Israeli military said in a statement after the strikes.

Hostilities have flared in recent months, including large demonstrations along the Gaza border and occasional rocket fire met by Israeli retaliatory strikes. But the tension had gradually ebbed after each incident.

CNN’s Ian Lee and Natalie Gallón contributed to this report.