Despite adding two centre-backs on deadline day for Premier League clubs, Leicester also resisted interest from Manchester United for England international Harry Maguire.
The two sides meet on Friday in the opening game of the Premier League season at Old Trafford.
In six seasons at Leicester, Vardy, 31, has scored 88 goals, and most memorably spearheaded the Foxes’ incredible Premier League triumph in 2015/16.
“Everybody knows how I feel about playing for this football club and it’s a great feeling to know that I can look forward to another four years as a Leicester City player,” Vardy said in a Leicester statement.
“The journey that me, the team and the club has been on over the past few years has been incredible. Going into the new season, it’s an exciting time for Leicester City and I’m delighted to be a part of it.”
Soyuncu, 22, joins from German side Freiburg in a deal worth a reported £19 million ($24.5 million), while Croatian under-21 international Benkovic will reportedly cost £13 million from Dinamo Zagreb.
The double swoop takes Leicester’s summer spending over £100 million after moves for Ricardo Pereira, Jonny Evans, James Maddison, Danny Ward and Rachid Ghezzal.
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