According to Hezbollah's Al Manar TV station, Dr. Aziz Asber was killed in an explosion in his car along with his driver several minutes after leaving his home.
Pro-Syrian government newspaper Al-Watan reported that Asber "died after an explosion targeted his car in the Hama countryside."
The attack on Asber was claimed by a Syrian rebel group affiliated to Tahrir al-Sham. It includes the group formerly known as the Nusra Front, which served as al Qaeda's Syrian branch.
The Abu Amara Brigades released a statement on their Telegram online channel that said they "planted explosive devices" which detonated and killed Asber.
An Israeli government official declined to comment on reports of Asber's death when asked by Reuters.
Asber was involved in Syria's chemical weapons development as well as in the Iranian Fateh missiles program. He worked on the development of medium- and long-range missiles.
He was considered a close associate of Syrian President Bashar Assad and worked directly under him, with no mediation. He also had close ties with Iranian and North Korean scientists.
One of the major projects Asber worked on was the conversion of the Iranian short-range ballistic missile, Fateh-110, into an M-600,the Syrian version of the missile.
According to reports, President Assad previously visited the department during his surprise visit in injured soldiers' homes in June 2017.
In addition to his missile development research, and his dark ties with North Korea and Iran, reports surfaced on Sunday that Asber was in direct contact with Hezbollah.
According to Al-Arabiya, the Syrian scientist was one of the few people who enjoyed the full confidence of the Lebanese terrorist organization in Syria.
It was also reported that Asber's work required coordinating between Iran and Hezbollah.
For this reason, the scientist was assigned the task of building warehouses for Hassan Nasrallah's organization in Syria.
It was also reported that in 2015 Dr. Aziz Asber published a eulogy letter to Hezbollah's military wing's Chief of Staff who was assassinated in Damascus in 2008.
To this day, Hezbollah claims that Israel is behind his assassination.
According to the IntelliTimes blog, Asber headed Department 4 at the Syrian Scientific Studies and Research Center in Masyaf, which is entrusted with the development and research of all of Syria's ballistic missiles and rocket programs.
He was the second senior scientist in the facility, answering directly to research center director Dr. Amr Armanazi.
Department 4 was entrusted with the activity of Institute 4000, which is responsible for the manufacturing of missiles and rockets.
Recently, according to opposition reports and satellite images, the department has been working to move some of Institute 4000's project to a new, safer location in the Masyaf area.
According to Al Arabiya, Israel has hit the Syrian Scientific Studies and Research Center in Masyaf with airstrikes in the past to foil Iranian military activity that has been taking place there for several years.
The latest reported Israeli strike in the area was on July 22, when Arab media reported IAF fighter jets attacked the research center's arms production center some six kilometers north of the new facility near Masyaf.
The Assad regime has yet to issue a statement on the attack.
Reuters contributed to this report.