Islamic Hamas movement on Wednesday said the killing of the commander of its military wing in Gaza was "a declaration of war" with Israel.

Israel "committed a dangerous crime and broke all redlines," said Fawzi Barhoum, a spokesman for Hamas, which controls the Gaza Strip. "The Israeli occupation will regret and pay a high price."

"The occupation has opened doors of hell against itself," Barhoum said.

A similar response was made by the Islamic Jihad, a smaller militant group, considering that the killing of Ahmed al-Jaabari was a declaration of war against the Palestinian people.

Al-Jaabari was killed along with another four, reportedly including his son, in an Israeli airstrike on their car Wednesday afternoon in Gaza City. Israel later launched a series of airstrikes in Gaza, killing two more people.