Getty ImagesSyrian media reports say Israeli warplanes have carried out dozens of attacks across the country, including in the capital, Damascus.
The UK-based Syrian Observatory for Human Rights (SOHR) said there were more than 100 strikes on military targets.
A research centre with suspected links to chemical weapon production was among the sites hit, according local media reports.
Israel says it is acting to stop weapons falling “into the hands of extremists” following the overthrow of the Assad regime.
Meanwhile, the UN Secuirty Council is meeting to discuss the situation in the country following the downfall of President Bashar al-Assad.
The SOHR says there have been hundreds of Israeli air strikes in the past two days, including on a site in Damascus said to have been used for rocket development by Iranian scientists.
The strikes come as the UN’s chemical watchdog warns authorities in Syria to ensure that suspected stockpiles of chemical weapons are safe.
According to the UN’s chemical watchdog, the Organisation for the Prohibition of Chemical Weapons (OPCW), a chemical weapon is a chemical used to cause intentional death or harm through its toxic properties, external.
The use of chemical weapons is prohibited under international humanitarian law regardless of the presence of a valid military target, as the effects of such weapons are indiscriminate by nature.
It is not known where or how many chemical weapons Syria has, but former President Bashar al-Assad is believed to have kept stockpiles and that the declaration he had made was incomplete.
Syria signed the OPCW’s Chemical Weapons Certificate in 2013, a month after a chemical weapons attack on suburbs of the capital, Damascus, that involved the nerve agent sarin and left more than 1,400 people dead.
The horrific pictures of victims convulsing in agony shocked the world. Western powers said the attack could only have been carried out by the government, but Assad blamed the opposition.
Despite the OPCW and the UN destroying all 1,300 tonnes of chemicals that the Syrian government declared, chemical weapons attacks in the country still continued.
BBC analysis in 2018 confirmed that between 2014 and 2018, chemical weapons were used in the Syrian civil war at least 106 times.
On Monday, the OPCW said it had contacted Syria “with a view to emphasising the paramount importance of ensuring the safety and security of all chemical weapons related materials and facilities” in the country.
Also on Monday, the Israeli military released photos of its troops who crossed from the Israeli-occupied Golan Heights into the demilitarised buffer zone in Syria where UN peacekeepers are based.
It comes a day after Israeli Prime Minister Benjamin Netanyahu announced that the military had temporarily seized control of the so-called Area of Separation, saying the 1974 disengagement agreement with Syria had “collapsed” with the rebel takeover of the country.
The Golan Heights is a rocky plateau about 60km (40 miles) south-west of Damascus.
Israel seized the Golan from Syria in the closing stages of the 1967 Six-Day War and unilaterally annexed it in 1981. The move was not recognised internationally, although the US did so unilaterally in 2019.
Speaking at a news conference on Monday, Saar said the Israel Defense Forces (IDF) was only making “a very limited and temporary step” taken for “security reasons”.
He also claimed that Israel had no interest in meddling in internal Syrian affairs and was concerned only with defending its citizens.
Defence Minister Israel Katz meanwhile said the Israeli military would “destroy heavy strategic weapons” – including missile and air defence systems.
The latest moves by Israel come after Syrian rebel fighters captured the capital, Damascus, and toppled Bashar al-Assad’s regime. He and his father had been in power in the country since 1971.
Forces led by the Islamist opposition group Hayat Tahrir al-Sham (HTS) entered Damascus in the early hours of Sunday, before appearing on state television to declare that Syria was now “free”.
On Sunday, Netanyahu branded the collapse of the Assad regime a “historic day in the Middle East”.
The Assad regime received much support from Hezbollah and Russia in the country’s brutal civil war. With Hezbollah involved in the Israel-Gaza war and cross-border air strikes between Israel and Lebanon, and Russia expending huge resources on its invasion of Ukraine, HTS, along with other rebel groups in Syria, were able to seize on the occasion and were ultimately able to capture large swathes of Syria.
During the 2011 Syrian uprising, Israel made the calculation that Assad, despite being an ally of both Iran and Hezbollah, was a better bet than what might follow his regime.
On Sunday, Netanyahu insisted Israel would “send a hand of peace” to Syrians who wanted to live in peace with Israel.
He said the IDF presence in the buffer zone was a “temporary defensive position until a suitable arrangement is found”.
“If we can establish neighbourly relations and peaceful relations with the new forces emerging in Syria, that’s our desire. But if we do not, we will do whatever it takes to defend the State of Israel and the border of Israel,” he said.
Israel is likely to be more sensitive over the Golan Heights, since HTS leader Abu Mohammed al-Jawlani’s family has roots there. Thousands of Israeli settlers now live in the area alongside about 20,000 Syrians, most of them Druze, who stayed on after it was captured.
Israeli strikes in Syria are nothing new. It has previously acknowledged carrying out hundreds of strikes in recent years on targets in Syria that it says are linked to Iran and allied armed groups such as Hezbollah.
The Israeli strikes in Syria have reportedly been more frequent since the start of the war in Gaza in October 2023, in response to cross-border attacks on northern Israel by Hezbollah and other groups in Lebanon and Syria.
Just last month, the Syrian Observatory for Human Rights (SOHR), a UK-based monitoring group, reported that a set of strikes hit a weapons depot and other locations in and around an area near Palmyra where families of Iran-backed militia fighters were, killing 68 Syrian and foreign fighters.
