3/6 KTo, unexpected river raise

[MarkL444]

Party Poker 3/6 Hold'em (8 handed)

Preflop: Hero is BB with K/images/graemlins/club.gif, T/images/graemlins/diamond.gif.
UTG folds, UTG+1 folds, MP1 folds, MP2 folds, CO folds, Button calls, SB completes, Hero checks.

Flop: (3 SB) 5/images/graemlins/club.gif, 3/images/graemlins/spade.gif, K/images/graemlins/heart.gif <font color="blue">(3 players)</font>
SB checks, <font color="CC3333">Hero bets</font>, <font color="CC3333">Button raises</font>, SB folds, Hero calls.

Turn: (3.50 BB) K/images/graemlins/diamond.gif <font color="blue">(2 players)</font>
Hero checks, Button checks. <font color="blue"> (failed c/r) </font>

River: (3.50 BB) 6/images/graemlins/diamond.gif <font color="blue">(2 players)</font>
<font color="CC3333">Hero bets</font>, <font color="CC3333">Button raises</font>, Hero...

a few hands earlier button open-limped from MP with KK, i raised TT LP, he just called heads up and waited till the flop to get aggressive.
is this a 3-bet?

[TheHip41]

I just call. Looks like you lost to Kings full, King with a better kicker, or a straight.

[Yeknom58]

I would call expecting to see a bigger kicker.