ISTANBUL

The killing of Iranian Supreme Leader Ayatollah Ali Khamenei by Israel on Saturday relied on years of covert surveillance, a human source and precision missiles fired from beyond Iran's air defense range, the Financial Times reported Monday, citing current and former intelligence officials.

According to the report, Israel concluded that Khamenei was at his compound based on its signal intelligence and confirmation from a human source from the US.

Israeli jets, which had been airborne for hours, fired approximately 30 precision munitions at Khamenei's compound, according to the report.

The missiles used were reportedly Sparrows, which can strike even small targets from more than 1,000 kilometers (621 miles) away -- beyond the effective range of Iran's air defenses, according to the report.

The strike was carried out in daylight, a deliberate choice, the Israeli military said, that allowed to achieve tactical surprise.

On the morning of the strike, Israel reportedly disrupted around a dozen mobile phone towers near Khamenei's compound, preventing his protection detail from receiving warnings.

According to the report, the lack of precautions on the part of the Iranians played a significant role in the success of the attack. A person speaking to a news site claimed that if Khamenei were in one of his two bunkers, Israel would be unable to reach him.

The operation that took place Saturday was also the result of intelligence work that had been ongoing for many years. According to the report, Israel had access to traffic cameras in Tehran, including those overlooking Khamenei's compound, and was monitoring movements in the area.

Israel also used social network analysis, a method for mapping relationships within large datasets, to identify targets and decision-making structures within the Iranian government.

Joint US and Israeli operations on Iran were launched Saturday and resulted in the killing of several Iranian officials and triggered retaliatory strikes against Gulf countries. Six US service members have been killed since operations began.