Israel’s military attacked 12 Syrian and Iranian targets in Syria on Saturday in a new wave of strikes it described as a ‘large-scale’ attack, following exchanges of fire earlier in the day sparked by an Iranian drone infiltration from Syria.

The military called the drone infiltration a “severe and irregular violation of Israeli sovereignty” and said Iran would be held responsible for its outcome, marking a dramatic escalation in tensions along its northern border.

The morning’s clashes also saw the crash of an Israeli F-16 jet after it was targeted by Syrian anti-aircraft missiles.

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Israeli aircraft “targeted the Syrian Aerial Defense System and Iranian targets in Syria,” a military statement said. “Twelve targets, including three aerial defense batteries and four Iranian targets that are part of Iran’s military establishment in Syria were attacked.”

Military spokesman Lt. Col. Jonathan Conricus said that during the attack 15-20 Syrian anti-aircraft missiles were fired towards aircraft, but did not hit them. Syria state TV said its air defenses responded to new Israeli raids.

The missiles triggered alarms that were heard in northern Israel.

“Syrians and Iranians are playing with fire,” Conricus said. “We are willing to extract a heavy price on anyone who attacks us.” He called that attacks on Iranian targets “quite significant.” However he stressed that “we are not interested in escalating the situation.”

Diplomatic sources said Israel has appealed to Russia to intervene and prevent further escalation. Similar calming messages were reportedly passed on to Washington.

The new Israeli raids came hours after an earlier one in central Syria.

The clashes erupted after an Iranian done infiltrated Israeli airspace and was downed by the air force. The army responded with strikes on Iranian targets, including the drone’s launch site — the Tiyas Military Airbase near Palmyra — which the army said it hit in “a complicated surgical strike.” The strike reportedly targeted a facility housing the unmanned aircraft’s Iranian operators.

The Syrian Observatory for Human Rights, a Britain-based monitor of the seven-year civil war, said the earlier Israeli raids had targeted several military bases in the east of the central province of Homs. It said the bases are used by both Iranian and Russian military personnel deployed in support of the regime.

Syrian state media said the later raids targeted military positions in the south of the country.

Conricus said the army had information on the drone’s mission, but would not go into details, saying only that it was “on a military mission sent and operated by Iranian military forces.”

Israeli warplanes flying over Syria met heavy anti-aircraft fire. The military said one of its pilots was seriously wounded as a result of an emergency evacuation from his F-16 jet targeted by missiles. The F-16 crashed in northern Israel. One pilot was evacuated to a hospital in serious condition. A second pilot was lightly wounded.

Watch: IDF pilot parachutes down after ejecting from aircraft

The confrontation was the most serious between Israel and Iran since the start of the civil war in Syria in 2011.

Sirens sounded in northern Israel throughout the morning as a result of massive Syrian anti-aircraft fire. Several Syrian anti-aircraft missiles reportedly fell inside Israeli territory, causing no damage.

Photos from Jordan showed the remains of anti-aircraft missiles that exploded in a field.

Syrian Air Defense missile fragments that landed in Jordan and Beqaa Valley. pic.twitter.com/IsANvKv0Hc via @aldin_ww — ARnews 1936 (@ARnews1936) February 10, 2018

IDF Spokesman Brig. Gen. Ronen Manelis said Israel held Iran directly responsible for the incident.

“This is a serious Iranian attack on Israeli territory. Iran is dragging the region into an adventure in which it doesn’t know how it will end,” he said in a special statement. “Whoever is responsible for this incident is the one who will pay the price.”

IDF Chief of Staff Lt. Gen. Gadi Eisenkot and Air Force chief Maj. Gen. Amikam Norkin were leading operations from army headquarters in Tel Aviv, with Prime Minister Benjamin Netanyahu holding security assessments and approving operations in real time.

By noon Defense Minister Avigdor Lieberman was convening the top brass at military headquarters in Tel Aviv to discuss a further response.

“The IDF is following events and is fully prepared for further action according to decisions and need,” the military said.

Tensions have been rising along the northern border recently, as Israel has warned repeatedly against Iranian efforts to set up weapons production facilities in Lebanon and establish a presence near the Israeli border with Syria.

Netanyahu has said that if Iran continues to try and entrench itself in Syria, Israel will “stop it.”

Early Wednesday morning, according to Syrian reports, Israeli aircraft bombed a military scientific research facility outside Damascus, which is suspected of both developing chemical weapons for Assad and assisting Iran and Hezbollah in improving their missile technology.

Meanwhile Hezbollah has been threatening to open fire at IDF soldiers if Israel does not halt the construction of a barrier it is building along the Israel-Lebanon border.