Kenaan, 63, who was head of Syrian military intelligence in Lebanon between 1982 and 2001, is the second senior Syrian official to end his life in five years. Former Prime Minister Mahmoud Zooby committed suicide in May 2000 in his home where he was held under arrest on charges of corruption.
The official Syrian News Agency, SANA, said Kenaan committed suicide in his office in Damascus.
Kenaan was interviewed along with other Syrian security officials by an international team investigating Hariri's Feb. 14 assassination in a massive Beirut blast.
He had contacted the Lebanese "Voice of Lebanon" radio hours before he committed suicide, saying "I believe this is the last statement that I can make." He said Syria has "a great interest" in uncovering the truth about Hariri's assassination, stressing that his testimony to the international investigators was aimed at "shedding light on the phase during which we served Lebanon."
Syria ended its military and intelligence presence in Lebanon last April 26.
In the early days of his career, Kenaan served as intelligence chief in several Syrian regions. In 2001 he was appointed as head of political security department and became Interior minister in 2004.
He was married and father of six.