The incident occurred on Friday at the couple’s home in Cairo, Egypt.
Egyptian police reported domestic staff at the couple's home as saying that Ayman al-Swidi, an Egyptian businessman, used a submachine gun to fire the fatal shots at his wife, 42, during a marital dispute.
Her body was found with 15 bullets in the chest and head, police said, after earlier saying that only four shots had been fired.
Swidi also killed the singer's manager, Khadiga Salahiddin and his own advisor, Amr Hassan Sabri, during the fracas at their apartment in the chic Zamalek area of the Egyptian capital.
Salaheddin and Sabri were themselves married.
Police said Swidi then took his own life, without giving further details. They have opened an inquiry into the killings.
Zikra's husband, Ayman al-Swidi,
killed two others and then himself
Friends close to the singer said the reason for the argument could have been Swidi's wish to move in permanently with his wife, something Zikra had resisted.
They also revealed that the couple had had an "unofficial marriage" for several years, but that Swidi obtained legal recognition for their marriage only two weeks ago.
However, the couple's cleaning lady also told police that Swidi suspected his wife of having an adulterous relationship with Sabri, and added that numerous rows between the two in the past had been sparked by the subject.
Zikra, a well-known figure in the Arab world, had lived in Egypt for several years.
Earlier this year a Saudi cleric caused outrage by calling for Zikra to face the death sentence after she compared her suffering to that of the Prophet Mohammed.
Zikra reportedly told a press conference in Qatar that the hardships she faced in launching her career were comparable to those endured by the prophet.