Dimuth Karunaratne played a patient and fighting knock, Sri Lanka v Bangladesh, 2nd Test, Colombo, 4th day, March 18, 2017. (AFP)

Opener Dimuth Karunaratne struck a half-century as Sri Lanka made slow progress in the second Test against Bangladesh in Colombo on Saturday.

The hosts reached 137-1 in their second innings by lunch on the fourth day to wipe out their 129-run first innings deficit and take an eight-run lead after they resumed on 54-0 at the P. Sara Oval.

Karunaratne remained firm with 67 not out -- his first half-century of the series -- which saw off the initial danger after Bangladesh got an early breakthrough in the second over of the morning.

Off-spinner Mehedi Hasan spun one sharply to bowl out Upul Tharanga for 26 on his first ball of the day but Karunaratne and Kusal Mendis shared 80 runs in an unbroken second-wicket partnership to put Sri Lanka in the driver's seat.

Mendis, who remained unbeaten on 36, survived a drop catch at the slip on 12 and a run-out chance just before the interval.

He top-edged Mehedi for a square leg boundary, bringing Sri Lanka the lead with five sessions still to play in the game.(AFP)