All Bangladesh will have to do now is to beat ICC associate members Uganda convincingly to advance to the Cup stage from Group A, also involving holders Pakistan.

Mehrab Hossain Jr was the hero with a brilliant all-round performance that helped the junior Tigers avenge their heart-breaking defeat against the same opponents in the last tournament at home.

Mehrab's occasional left-arm spin saw the man-of-the-match return with a haul of 4-29 before he hit an unbeaten 38 to steer Bangladesh victory after being reduced to 78-5 while chasing New Zealand's 175 at the P Saravanamuttu Stadium.

New Zealand opening pair Todd Astle (44) and Martin Guptill (28) made a good start putting on 57 after Bangladesh captain Mushfiqur Rahim invited them to bat first. But they had little answer once the slow bowlers, one of the strongest departments of the Bangladesh team, took charge.

New Zealand were well placed to set a fighting total at 140-5 but Mehrab and fellow left-arm spinner Sohrawardi Shuvo ripped through their tail, dismissing the last five batsmen for 35 runs.

Shuvo claimed three wickets for 36 while Nabil Samad, another left-arm slow bowler, produced the most economic figure conceding 18 runs from eight overs.

Bangladesh, however, fell in big trouble as their formidable top order including dashing Tamim Iqbal (3), Raqibul Hasan (18), Mehdi Hasan (0), dependable Sakib Al Hasan (13) and Shamsur Rahman (30) departed with the scoreboard reading 78.

But Mehrab received good support from the tail including a 45-run sixth wicket stand with skipper Rahim, the only Test player in the squad, to coast to 176-7 with more than a dozen overs to spare.

Rahim made 26 off 47 balls, Shuvo added a 31-ball 18 and Sirajullah Khadem was not out with 10 runs.

Tigercricket.com adds: "Mehrab was brilliant. He held the innings together after we lost Shamsur and Raqibul, two set batsmen, in the space of two overs. He took no unnecessary risks and played on singles and twos," said Bangladesh team's assistant coach Nazmul Abedin Fahim over phone from Colombo.

Fahim also informed that the wicket at the P Sara had remained under cover throughout Saturday and the night before because of rain.

"It had a lot of moisture and grass and there was good bounce and seam movement. It was more like New Zealand conditions and their opening bowlers Bennett and Southee really bowled well. We lost the first three wickets to them but it would not have been a surprise if they had taken more wickets in their opening spell," added Fahim.

Bangladesh will play their next group match against Pakistan on February 8.

In the day's other matches, Australia (316-9) rode on Tom Cooper's 104 to outclass South Africa (141) by 175 runs, Zimbabwe (215-7) thrashed Ireland (97) by 118 runs and hosts Sri Lanka (187-6) managed a four-wicket victory against Scotland (186).