Palestinians in the Gaza Strip fired two rockets at Israel on Friday evening, the military said. The rockets apparently fell in open areas and there were no immediate reports of casualties or damage.

Israel Defense Forces aircraft carried out retaliatory strikes against Hamas targets in Gaza, the army said.

Rocket warning sirens sounded in communities near the Gaza Strip, sending thousands of residents to bomb shelters as they were celebrating the Shabbat evening meal.

One rocket landed in an open area in the Sha’ar Hanegev region, while the second apparently fell within the Strip.

The IDF said in a statement that it had carried out airstrikes in response to the rocket fire.

“A short while ago, IDF fighter jets targeted Hamas terror targets in the southern Gaza Strip,” the IDF said in a statement.

“During the strike, a rocket manufacturing workshop and a weapons manufacturing facility belonging to the Hamas terror organization were struck. This strike will impede the Hamas terror organization’s future abilities,” the statement said. “The IDF views any kind of terror activity aimed at Israel with great severity and will continue operating as necessary against attempts to harm Israeli civilians.”

The IDF said it holds Hamas responsible for all events in the Strip and emanating from the territory, and that the terror group would “bear the consequences” for attacks against Israel.

Palestinian media reported IDF strikes in the southern and central areas of the Strip.

In an immediate response, an IDF tank fired a shell at a Hamas observation post to the east of Deir el-Balah in central Gaza, Hamas-linked al-Resalah news reported.

Later, Hamas-linked media reported IAF strikes on a Hamas military site west of Khan Younis in the southern Gaza Strip. Loud explosions were heard in the area. There was no immediate confirmation from the IDF.

The activation of the sirens came a day after the Hamas terror group, which rules Gaza, warned that Israel’s potential annexation of West Bank lands next week would be a “declaration of war.”

Besides the issue of annexation, there have also been tensions between Israel and Gaza-based terror groups over delays in the transfer of Qatari aid money to Gaza.

This was the first rocket fired into Israel in 10 days.

In recent days, Hamas and the Palestinian Islamic Jihad, the two most powerful terror groups in Gaza, have threatened to step up clashes along the border, following months of relative calm in the area.

Israel’s planned annexation of parts of the West Bank constitutes a “declaration of war,” a spokesperson for Hamas’s military wing, the Izz al-Din al-Qassam Brigades, said in a speech on Thursday.

“The resistance considers this decision to be a declaration of war upon the Palestinian people. The resistance will be the loyal and dutiful guard of the people throughout this war, acting in defense of our people, our land, and our holy sites. We will make the enemy bite his fingers in remorse for this sinful decision,” the spokesperson, known by his nom de guerre Abu Obeida, said in the speech.

“And those who oppress will come to know by what overturning they will be overturned,” Abu Obeida continued, citing a verse from the Quran.

On Friday, a senior Hamas official reiterated the message, saying Israel and Hamas were locked in an “existential struggle.”

“This is an existential struggle. It is either us or this entity,” said Salah al-Bardawil speaking at a rally in Gaza. “[Israel] must realize that yesterday’s statement by the al-Qassam brigades will become reality.”

Defense Minister Benny Gantz fired back hours later in a warning to Hamas leaders.

“I suggest they remember that they’ll be the first ones to pay for any aggression,” he said during a ceremony for graduates of the air force’s pilot course. “The IDF is the strongest army in the region and the price for any attempt to harm Israeli civilians will be strong and painful.”

Prime Minister Benjamin Netanyahu’s annexation plan, which is slated to be launched as early as July 1, has provoked widespread international criticism. But Israel’s volatile border with Gaza has remained relatively quiet. Demonstrations have been held in the Strip against the plan and a lone rocket was fired from Gaza into Israel last week, landing in an open field and causing no casualties. But Hamas and Israel have so far avoided a serious — and potentially deadly — escalation.

In recent months, Israel and Hamas have been negotiating a possible prisoner swap and long-term ceasefire agreement, so the terror group has largely maintained calm along the Gaza border.

Israel and Hamas have in the past failed to advance in the talks, in part because each has demanded a different timetable.

Hamas has demanded two rounds of prisoner releases — the first in exchange for information on the captives, the second in exchange for the actual delivery to Israel of the captives and the remains of soldiers Oron Shaul and Goldin, whose bodies are believed to be held by the terror group since they were killed in the Strip during the 2014 war known in Israel as Operation Protective Edge.

Israel has refused, insisting that any deal must take place in a single exchange.