"I feel a huge sadness about this whole situation. Alex has been my friend and mentor for almost thirty years and his contribution to the SNP and the independence movements speaks for itself. While the decision to resign has been Alex's alone, I understand why he has chosen to separate the current questions he is facing from the day to day business of the SNP and the ongoing campaign for independence," Sturgeon said in a statement.
However, the complaints received by the Scottish government could not be ignored and required investigation irrespective of the seniority of the official involved, the first minister added.
"In the meantime, I agree with Alex that the cause of independence, to which both he and I have dedicated our entire lives, is bigger than any one individual. And the work we must do to achieve independence is more important now than ever," Sturgeon said.
Salmond, who had been an SNP member for 45 years, 20 of them as party leader and seven as the first minister of Scotland, announced his resignation on Wednesday.
For centuries, Scotland has been seeking independence from the United Kingdom; however, the secession referendum in 2014 resulted in 55 percent of Scots choosing to remain in the union with London. In March 2017, the Scottish parliament backed Sturgeon's proposal to ask for the second independence referendum between fall 2018 and spring 2019, but the proposal was rejected by London citing Brexit as a more pressing item on the agenda.