Namibia scored a nerve-shredding victory over Oman in their T20 World Cup Group B clash in Barbados on Sunday after a low-scoring thriller was decided by a super over.

David Wiese was the hero for Namibia, contributing 13 runs in the Africans' super over total of 21 before then restricting Oman to 10 runs with the ball in hand to seal a crucial win at Kensington Oval.

The match had gone to a decisive extra over after a tense duel saw both teams finish with 109 runs from their allotted 20 overs.

Oman had looked to be heading for defeat after a superb four-wicket bowling display from Ruben Trumpelmann saw them all out for 109 off 19.4 overs.

But Oman's bowlers responded with a disciplined performance to contain Namibia's bats, with Mehran Khan conjuring a superb spell to leave the match on a knife edge.

Khan finished with figures of three wickets for seven runs off three overs.

The veteran Oman bowler took two wickets in the final over to frustrate Namibia, who had needed just five runs from the over to clinch victory.

But Khan was bizarrely overlooked for the super over bowling duties by Oman, with Bilal Khan handed the ball instead.

That move backfired spectacularly, though, with Wiese blasting a four off the first ball and then crushing a full toss for six off Khan's second delivery.

Wiese took three more runs off the next two balls before Namibia skipper Gerhard Erasmus hit back-to-back fours to set Oman a daunting victory target of 22 off their super over.

Wiese took over the bowling duties for Namibia and after conceding just two runs from his first two deliveries, took the wicket of Naseem Khushi.

Two more singles left Oman needing 18 from the last delivery to win, meaning Wiese could allow Zeeshan Maqsood to blast a six knowing victory was assured.

"I definitely aged a couple of years tonight," the 39-year-old Wiese said. "And I don't have a lot of years left in me. It was an emotionally draining evening."

Wiese said he had been confident of steering Namibia to victory with bat and ball in the super over.

"It helped that I had a feel of the game and knew if I get a few hits out in the Super Over .... then with the ball, felt like taking the ball and executing.

"The pitch was difficult and didn't play the way we thought. But we adapted well."

Oman captain Aqib Ilyas was left lamenting an agonising near-miss -- but defended the decision to opt for Bilal as the super over bowler over the in-form Khan.

"I think Bilal is one of the best bowlers you can have at this level," Aqib said. "But there are days where you plan and it doesn't execute.

"He was clear, we were clear, but maybe the ball was wet and he couldn't execute."

Earlier, Trumpelmann had given Namibia a dream start with two wickets from the first two deliveries of the match, part of a four-wicket performance. Wiese also impressed in the regulation 20 overs with 3-28 off 3.4 overs.

Namibia made hard work of the run chase, however, with Jan Frylinck (45) and Niko Davin (24) top scoring as the southern Africans came up just short of their victory target.