Gylfi Sigurdsson has warned Iceland must be wary of his former training partner and golf buddy Harry Kane when they face England in the last 16 of Euro 2016.

Swansea City midfielder Sigurdsson helped Heimir Hallgrimsson and Lars Lagerback's side to an unforgettable last-gasp 2-1 win over Austria at the Stade de France that secured second place in Group F and eliminated their opponents.

Like Iceland, England are through as group runners-up with five points from three matches and their form in front of goal is a cause for concern, with Kane short of his stellar Tottenham form in the 1-1 opener against Russia before being substituted at half-time during the eventual 2-1 win versus Wales.

Sigurdsson spent two seasons at White Hart Lane before beginning a second spell at Swansea in 2014-15 and, even though Kane was living on a diet of sporadic appearances and loan spells ahead of his breakthrough, the 26-year-old recognised his friend as a talented performer.

"He was very good back then, we did a lot of training sessions together and shooting drills afterwards," Sigurdsson said. "You never know what's going to happen, but he has scored an incredible amount of goals for Tottenham in the last couple of years.

"And especially after the first season, you never know what will happen in the second. But he has shown he is a fantastic finisher and he has become one of the leaders at Tottenham. That shows the character he has and the person he is.

"I can't say that he came to me for advice. Of course we were good friends, we played golf together. It could have been anyone but we did do shooting after training together.  It just happened to be me doing it with him.

"He was very focussed on what he wanted. He's a humble guy, very down to earth and really likes his football. 

"I think that's what got him through in the end. Of course he didn't get his chance until three years ago. But he hit the ground running and scored many goals in his first full season, and more in the second. He is a fantastic guy.

"It is hard to judge if a young player is going to become that big when they get their chance, but he's done incredibly well."

Sigurdsson insists he is the better golfer and claims Kane "would be lying" if he said otherwise but on the football pitch he recognises the 22-year-old's mental strength as an asset that will allow him to overcome a dry spell to date in France.

"His mentality will be that he is going to score in the next game," Sigurdsson explained. "That's the way he is. 

"That is what happens when goalscorers don't score - they get the extra pressure and [people asking] 'what's up with them, blah, blah, blah'. 

"He is the kind of guy who doesn't get too high when he scores and doesn't get too low when he doesn't score. He just keeps a level head and that's why he will score goals throughout his career."

England boss Roy Hodgson named five Tottenham players in his starting XI for the opening two games of the tournament and Sigurdsson is looking forward to an instance of friends reunited in Nice.

"Yes I still speak to a few of them," he added. "I will certainly send them a few texts. It's a game that couldn't be more appropriate for us."