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The commander of Iran's intelligence service in Syria and four of his colleagues were killed on Saturday in an Israeli strike in Damascus, which shattered an upmarket, diplomatic quarter of the city.
Haj Sadiq Ameed Zada and his deputy Haj Gholam were among the five Iranians killed in the Syrian capital, Iran's Islamic Revolutionary Guard Corps said.
Residents reported four powerful explosions, which flattened a four-storey apartment complex where the Iranian officials lived.
The Syrian Observatory for Human Rights said 10 people, including Syrian civilians, were killed. Extensive damage to nearby cars and shops showed the extent of the strike, in the city's Mazzeh district.
Iran's President Ebrahim Raisi said Israel's attack in Syria will not go "unanswered".
Earlier Iran's Foreign Ministry spokesperson Nasser Kanaani said the strike was a “desperate attempt to spread instability in [the] region”.
“Iran … reserves its right to respond to the organised terrorism of the fake Zionist regime at the appropriate time and place.”
There was no immediate comment from Israel. The country rarely acknowledges its attacks and activities in Syria.
The strike risks ratcheting up tensions between the Middle Eastern adversaries as Israel continues to pursue its war against Hamas in the Gaza Strip.
It also follows an attack this week by Iran, on what it said was an Israeli spy base in Iraq.
A Syrian military source said at about 10.20am, “the Israeli enemy carried out an air attack from the direction of the occupied Syrian Golan, targeting a residential building in the Mazzeh neighbourhood in the city of Damascus”.
“Air defence assisted in repelling the aggression and some missiles were shot down. The aggression resulted in the martyrdom and injury of a number of civilians, the destruction of the building and damage to the neighbouring buildings,” the source said.
The attack caused a large plume of smoke to billow into the sky. Civil defence personnel were busy searching for survivors under the rubble of the collapsed building.
A member of the Syrian civil defence told The National: “We are still searching for bodies and victims in the rubble. The attack destroyed the entire building and there are civilians in the building as it is a residential building.
“We don’t know how many people are dead or alive. As of now, there are five killed, but we hope to still find people alive in the wreckage.”
A local resident said: “This is a very peaceful area and there are rarely any issues here.
“We heard an enormous explosion, and another followed. There were several after and we saw the smoke emerge.
“It happened in broad daylight. In the morning, many people were just going about their business. It’s a residential place. There aren’t any heavy things happening here.”
Cars were damaged, as were shops and an entire building complex, the resident said.
“Why can’t they just leave us alone? They are attacking Gaza, Syria, Yemen, everywhere and every day Israel attacks somewhere new.”
The targeted building was not known as a centre of operations used by Iranian intelligence or military advisers.
The strike follows an attack this week by Iran on what it said was an Israeli spy base in Iraq.
The western neighbourhood of Mazzeh is home to several diplomatic missions, including the Lebanese and Iranian embassies.
“An attack resulted in the destruction of a residential building in Mazzeh by an Israeli aggression,” Syrian state media Sana said.
A security source, part of a network of groups close to Syria's government and its major ally Iran, said the building was used by Iranian advisers supporting President Bashar Al Assad's government, and that it was entirely flattened by “precision-targeted Israeli missiles”.
A meeting of leaders with close ties to Iran took place at the building that was destroyed in the attack, the British-based war monitor Syrian Observatory for Human Rights said.
Since the Israel-Gaza war started in early October, rockets have been fired from Syria into northern Israel and the Israeli-occupied Golan Heights.
This has increased tensions along the Lebanon-Israel border and attacks on ships in the Red Sea by Yemen’s Iran-backed Houthi rebels.
