Hamas and Palestinian Islamic Jihad's statement said the groups' military wings were jointly responsible for firing dozens of mortars and some rockets at Israel starting Tuesday morning and lasting all through to the evening—even increasing between 8pm and 9pm.
Schools in Israeli communities around Gaza will operate as usual, until further notice. A final decision on the matter, however, will be made early Wednesday.
"The Izz ad-Din al-Qassam Brigades and Al-Quds Brigades take responsibility for bombing military targets and communities in the vicinity of Gaza with dozens of rockets throughout the day," the statement said.
"This was a response to the Zionist aggression and the crimes against our people and the members of the resistance, the last of which was attacking the two military wings' outposts—which led to the deaths of several of the combatants therein," the message continued.
"The action was added to the enemy's crimes against our people in the Marches of Return along the strip," the terror groups stated, before accusing Israel of starting the latest round of hostilities in an attempt to "get out of paying for its crimes against the peacefully protesting civilians."
"Our retaliation today was a statement that these crimes could not be accepted silently. The resistance is waging a campaign against Israel in a manner serving the interests of the Palestinian people and will not allow (Israel) to force new equations of bloodshed," the statement went on to say.
"We warn Israel against continuing to attack our people. All options are open to the resistance—bombings will be met with bombings and blood with blood. We will adhere to this equation—no matter the cost," Hamas and Palestinian Islamic Jihad vowed.
The combative statement aside, Palestinian Islamic Jihad later admitted to holding talks with Egypt around achieving calm in the strip's border, but did note its reply to Egypt was that it will "respond to any Israeli aggression."
"The action of Hamas's Izz ad-Din al-Qassam Brigades and and Islamic Jihad's Al-Quds Brigades proves the unity on the ground and reflects the existence of a joint operations room for the resistance, which orchestrates, plans and carries out the actions," the terror group added.
The Palestinian Authority issued a statement of its own Tuesday evening, demanding "urgent international intervention to stop the Israeli aggression in the Gaza Strip."
IDF Spokesman Brig.-Gen. Ronen Manelis told reporters at the IDF's Kirya headquarters in Tel Aviv earlier that Tuesday's events constituted a "serious terror attack against the State of Israel."
"We will not allow it," he added. "This is a loss of control by Hamas—after failing in its attempts to cross the fence and carry out attacks, it chose the route of projectile terrorism."
As a result, Manelis elucidated, the army carried out the most "significant strikes" since 2014's Operation Protective Edge with three waves of attack throughout the day hitting dozens of terror targets.
Manelis also mentioned the strikes' objectives, namely the terror groups' command centers, arms manufacturing sites, training camps and and an irregularly large terror tunnel.
"The strikes will only grow stronger if the fire continues," the spokesman warned. "We have no intention of stopping the strikes if the terror continues as it has in the past few hours, and I assume we'll see a growth in the IDF's response."
"The strip's terrorists know full well which assets they lost today," the senior officer assured, "and the fact that Hamas and Islamic Jihad's leaders have been in hiding since the morning is a testament to their understanding of the army's capabilities."
Manelis then noted that further Home Front Command instructions will be issued late Tuesday and Wednesday and added that the army was "prepared for a wide variety of scenarios in all sectors."
"Today's epicenter is the Gaza theater," he continued, "where most of our forces are stationed, and we are determined to return calm and security to the people residing in communities around Gaza."
"So long as terrorism exists, we endeavor to stop it," the spokesman announced, saying that in the past few weeks the IDF killed more than 120 terrorists near the fence.
Questioned whether the IDF was preparing to call in reservists to bolster its forces, he replied, "We will act as required. We are prepared for a wide variety of scenarios based on our regular forces."
Liad Osmo, Elior Levy, Yoav Zitun and Matan Tzuri contributed to this report.