Harry Kane fired Tottenham past third-tier Portsmouth and into the FA Cup fourth round on Saturday as 2021 winners Leicester emerged unscathed from a tricky tie against lowly Gillingham.

Elsewhere on a packed day of third-round action, Southampton came from behind to beat Crystal Palace 2-1 in an all-Premier League tie.

Antonio Conte rang the changes for Spurs for the match against League One Portsmouth but retained a heavyweight forward line including Kane and Son Heung-min.

The in-form Kane broke the deadlock in the 50th minute, receiving the ball on the edge of the box and bending a fine curled effort past the despairing dive of Josh Griffiths.

The England captain, with four goals in four matches since the World Cup, now has 265 goals for Spurs -- just one behind the club's all-time record scorer, Jimmy Greaves.

Spurs, who have won the FA Cup eight times, were unable to add to their tally but saw out the match fairly comfortably.