It was late in the evening of 1 August 2008 in the Syrian coastal city of Tartous when the sniper fired the fatal shot. The target was General Muhammad Suleiman, President Bashar al-Assad's top security aide. Israelis, the US embassy in Damascus reported, were "the most obvious suspects" in the assassination.

US state department cables released by WikiLeaks trace the panicked response of the authorities. "Syrian security services quickly cordoned and searched the entire beach neighbourhood where the shooting had occurred," the embassy was informed. Syrian-based journalists were instructed not to report the story. It was a sensational event, akin to another mysterious assassination in Damascus earlier that year, when a car bomb killed Imad Mughniyeh, military chief of Hezbollah.

Initial reports were vague about Suleiman's identity and position, and the news blackout lasted for four days. But the US government knew exactly who he was. A secret document several months earlier gave his precise job description: "Syrian special presidential adviser for arms procurement and strategic weapons."

Eleven months earlier, Israeli planes had attacked and destroyed a suspected nuclear site at al-Kibar on the Euphrates river, apparently one of the special projects Suleiman managed "which may have have been unknown to the broader Syrian military leadership", as the embassy put it. Israeli media reported that he had also served as Assad's liaison to Hezbollah.

Israel was the obvious suspect in Suleiman's murder, US officials reported. "Syrian security services are well aware that the coastal city of Tartous would offer easier access to Israeli operatives than would more inland locations such as Damascus. Suleiman was not a highly visible government official, and the use of a sniper suggests the assassin could visually identify Suleiman from a distance."

In the capital, the government remained silent, probably, the embassy speculated, because "(1) they may not know who did it; (2) such accusations could impair or end Syria's nascent peace negotiations with Israel; and (3) publicising the event would reveal yet another lapse in Syria's vaunted security apparatus."

Reports about internal discussions suggest that the Tartous killing strengthened the hands of Syrian security officials who were opposed to peace talks with Israel.

Ten days later a US embassy contact reported that the assassination had become "a frequent source of controversy" in internal Syrian government deliberations. "Tempers flared during an August 12 higher policy council meeting when high-level security service officials openly questioned the government's continuation of indirect negotiations with Israel and its 'generosity' with Lebanon." Security chiefs claimed that Syria would make concessions and not receive any tangible gains from engaging Lebanon or talking indirectly to Israel.

"Underlying this tense exchange was frustration within the security services that the [Syrian government] was all but ignoring the assassination of Suleiman. Security service officials were suggesting that 'if the Israelis did it' [killed Suleiman], why was the Syrian government continuing the dialogue?" the embassy source added. "'And if it was an inside job, people are wondering about their future.'"

Assad was thus under increasing pressure to provide assurances to his security chiefs about their positions and about the government's intention not to make premature concessions.

Embassy cables also show that the US had previously wanted to apply financial sanctions to Suleiman as part of an effort to weaken the Assad regime, but found it difficult to do so because the information about him was so highly classified it could not be made public.

"Muhammad Suleiman is a relatively low-payoff target," diplomats reported back to Washington. "His activities are not widely known, which will make it difficult to obtain unclassified information for a public statement and, likewise, make it unlikely that his designation would resonate inside Syria."