Islamic Jihad and Hamas on Tuesday vowed to avenge the killing of an Islamic Jihad commander in the Gaza Strip overnight, even as Israel called for Hamas to remain out of the conflict.
A joint statement from the two terror groups indicated that Hamas would contribute to any response to the death of Baha abu al-Atta.
"Israel bears full responsibility for the heinous crime and it will not go unanswered," the groups said.
"Israel's attempt to resolve its internal crises at the expense of Palestinian blood will not work. Returning to the policy of assassination is a red line. The factions are capable of disrupting Israel's plans and setting the rules of the struggle."
Israel had urged Hamas to refrain from joining Islamic Jihad in firing rockets at its civilian population after the IDF targeted assassination of Baha Abu al-Atta.
An Israeli source said that Israel conveyed the clear message via Egypt and UN envoy Nikolai Mladenov.
"If you join in - the IDF will attack you, you do not - the IDF will not attack you," the message read.
Israel has suffered repeated rocket strikes since the assassination. Sirens have sounded across southern and central Israel since early Tuesday.
The IDF said Tuesday that by 9.30am, 50 rockets had been fired and 20 of those were intercepted by the Iron Dome missile defense system.
All educational institutions in the south and center were closed Tuesday and people in non-essential professions were told to stay home from work.