JERUSALEM – Militants in Gaza fired about 20 rockets into Israeli territory Sunday evening, hours after a Palestinian news agency released a graphic video clip that shows an Israeli army bulldozer dragging the body of a Palestinian man who the military said was a terrorist killed while placing an explosive device along the border.

The increase in tension comes after weeks of relative quiet as Egypt attempts to broker a long-term truce between Israel and Hamas, the militant Islamist faction that rules the Gaza Strip. Israel and Hamas have fought three wars over the past decade, but there have been numerous other flare-ups in violence.

It also comes a week before Israelis return to the polls for an unprecedented third general election in less than a year. Over the weekend, Prime Minister Benjamin Netanyahu’s handling of the long-running Gaza situation came under sharp criticism.

In a statement, the Israeli military said 21 projectiles and rockets were fired from Gaza on Sunday. Thirteen were intercepted by the Iron Dome aerial defense system. Videos shared on social media showed civilians in the cities of Ashkelon and Sderot crouching for cover as warning sirens blared in most of the Israeli communities that surround Gaza.

In Gaza, emotions were intense after the video clip – filmed by al-Hadath, a news agency based in Ramallah, West Bank – showed the Israeli military bulldozer scooping up the body. An army tank is seen accompanying the bulldozer in the video, which was shared widely on social media.

Hamas and the Palestinian Islamic Jihad issued statements condemning Israel’s actions and swore revenge. The dead man was identified as Mohammed al-Naem, a member of the Islamic Jihad, the second-largest militant faction in Gaza after Hamas. Abu Hamza, a spokesman for the group’s armed wing, the al-Quds Brigade, said Israeli military vehicles had entered Gaza, and he warned there would be consequences.

Hamas spokesman Fawzi Barhoum said that Naem was killed deliberately and that he had been “defenseless.”

“The abuse of his body right before the eyes of the entire world is a heinous crime that can be added to the other crimes against our people,” Barhoum said.

Islamic Jihad took responsibility for the rocket fire, saying it was in response to the man’s killing.

The video also drew criticism inside Israel, with human rights groups calling on the military to immediately open an investigation into the incident.

Adalah – the Legal Center for Arab Minority Rights in Israel said in a letter to the army’s legal representative that, according to international statutes, the actions “depicted in the video were viewed as war crimes and blatant violations of international criminal law, and international human rights and humanitarian law.”

On Twitter, Defense Minister Naftali Bennett defended the army’s actions, writing that it “killed a terrorist and collected his body.”

“This is how it should be done, and this is how it will be done,” he wrote.

Some far-right leaders, including Bennett before he became defense minister, have been vocal in calling for Israel to respond with greater force to the rocket fire and other acts of violence emanating from Gaza. There has been fierce criticism of what appears to be an attempt by Netanyahu to reach a long-term understanding with Hamas.

On Saturday, Avigdor Liberman, Israel’s hawkish former defense minister, revealed that Netanyahu had sent the head of Israel’s Mossad intelligence agency to Doha, Qatar, earlier this month to ask the gulf state to continue sending emergency funds to the impoverished Gaza Strip. And last week, Israel announced steps to increase the number of entry permits for day laborers from Gaza and enlarge the fishing zone for Palestinian fishermen.