Pakistan became the first team to reach the Twenty20 World Cup semi-finals after beating Namibia by 45 runs, with brilliant half centuries from Mohammad Rizwan and skipper Babar Azam in Abu Dhabi on Tuesday.

Rizwan finished with a slow-to-fast 50-ball 79 not out while Babar notched his 23rd Twenty20 international fifty with a 49-ball 70 to lift Pakistan -- who won the toss and batted -- to 189-2 in their 20 overs. 

Namibia tried their best to match their opponents, with David Wiese notching 43 not out and Craig Williams scoring 40, but Pakistani bowlers never allowed them a free hand as they managed 144-5 in 20 overs.

With four wins in as many games, Pakistan became the first side to reach the last four from Group 2. This will be their fifth semi-final in Twenty20 World Cup history -- the most by any team.

Williams knocked five boundaries and a six before he holed out to spinner Shadab Khan while Wiese smashed two sixes and three boundaries in his 31-ball knock.

Opener Stephan Baard scored 29.

Babar said Pakistan went with a different plan, batting first.

"It was a different plan today, wanted that opening partnership to go deep and it worked for us," said Babar. "Rizwan was superb in the final few overs.

Pakistan skipper was confident his team will keep the winning momentum.

"Everything has gone according to plan, we're looking forward to the semi-finals and playing our cricket with the same intensity."

Namibia skipper Gerhard Erasmus admitted his side was outplayed.

"We knew from the start that Pakistan are of high quality, they look like title contenders, we knew we'd have to compete hard and I thought we did that for quite a while but in the end it was not enough," said Erasmus.

Rizwan and Babar were the stars once again, like they were in Pakistan's win over arch-rivals India, which gave them a kick-start to the event.

The pair added 113 for the first wicket after Pakistan were slow out of the blocks, scoring just 59 in the first ten overs but ended with a flurry in the next ten, taking 130 runs.

Veteran Mohammad Hafeez scored a brisk 16-ball 32 not out with five boundaries.

Pakistan's total is the second-highest in this tournament, behind Afghanistan's 190-4 against Scotland in Sharjah.

Babar hit seven boundaries before he holed out to David Wiese in the 15th over while Fakhar Zaman was smartly caught by keeper Zane Green for five.

Rizwan reached his tenth half century with a pulled six off Wiese in the 19th over before hitting four boundaries and a six to take 22 off JJ Smit's final over.

Rizwan's knock included eight fours and four sixes.

Pakistan next face Scotland in their last match in Sharjah on Sunday. Namibia will meet New Zealand, also in Sharjah two days earlier.

Pakistan vs Namibia T20 World Cup scoreboard

Pakistan

Mohammad Rizwan not out               79

Babar Azam c Frylinck b Wiese         70

Fakhar Zaman c Green b Frylinck        5

Mohammad Hafeez  not out              32

Extras: (lb3)                          3

Total: (for two wkts; 20 overs)      189

Did not bat: Shoaib Malik, Asif Ali, Shadab Khan, Imad Wasim, Hasan Ali, Haris Rauf, Shaheen Shah Afridi 

Fall of wickets: 1-113 (Babar), 2-122 (Zaman)

Bowling: Trumpelmann 4-1-36-0, Wiese 4-0-30-1, Smit 4-0-50-0, Frylinck 4-0-31-1, Shikongo 2-0-19-0, Loftie-Eaton 2-0-20-0,

Namibia

S. Baard run out                      29

M. van Lingen b Hasan                  4

Craig Williams c Hasan b Shadab       40

G. Erasmus c Shadab b Imad            15

D. Wiese not out                      43

JJ Smit c Zaman b Rauf                 2

J. Loftie-Eaton not out                7

Extras: (lb2, nb1, w1)                 4 

TOTAL (for five wkts; 20 overs)      144       

Did not bat: R. Trumpelmann, Z. Green, J. Frylinck, B. Shikongo 

Fall of wickets: 1-8 (Lingen), 2-55 (Baard), 3-83 (Erasmus), 4-93 (Williams), 5-110 (Smit)

Bowling: Shaheen 4-0-36-0 (1nb), Hasan 4-0-22-1, Imad 3-0-13-1, Rauf 4-0-25-1 (1w), Shadab 4-0-35-1, Hafeez 1-0-11-0

Result: Pakistan won by 45 runs