Despite a huge outlay last summer, which saw the likes of Radamel Falcao and James Rodriguez join, Monaco are 13 points adrift of leaders Paris Saint-Germain, with only six games remaining.
However, Vasilyev revealed he is happy with the job that Ranieri is doing, and rubbished reports he will be relieved of his duties.
"The rumours amaze me," Vasilyev told the club's official website.
"I have already said Claudio Ranieri is under contract until June 2015.
"(He) works extremely hard with all his staff to achieve the objectives set at the beginning of the season.
"These rumours are not justified."