Sarfraz Ahmed scored Pakistan's first World Cup century since 2007 to lead his team into the quarter-finals with a seven-wicket romp past Ireland at the Adelaide Oval on Sunday.

Left-armer Wahab Riaz took three wickets and fellow-seamers Sohail Khan and Rahat Ali snared two apiece as Ireland, electing to bat, were shot out for 237 despite skipper William Porterfield's 107.

The modest target was overhauled in 46.1 overs as Sarfraz returned unbeaten on 101 to emulate Imran Nazir's 160 against Zimbabwe in Jamaica in 2007, the last hundred hit by a Pakistani batsman in a World Cup.

The match ended in a farce as Umar Akmal played out five dot balls when five more runs were needed so that Sarfraz, then on 97, could reach his century.

Sarfraz duly obliged in Paul Stirling's next over hitting a boundary and then himself defended four balls to allow Akmal to hit the winning runs in the subsequent over.

Pakistan finished third in Pool B behind defending champions India and South Africa, while the West Indies took the fourth place following a six-wicket win over the United Arab Emirates in Napier earlier on Sunday.

Pakistan take on four-time champions and Australia in the quarter-final in Adelaide on March 20, while the West Indies travel to Wellington to play co-hosts New Zealand on March 21.

Ireland, the last surviving non-Test nation in the fray, paid dearly for a miserable batting display in which Porterfield played a lone hand with 11 boundaries and a six.

The first four wickets fell for 134 runs by the 30th over as none of the top order crossed 20 on a slow pitch. 

Wicket-keeper Gary Wilson's 29 was the next highest score before the Irish were bowled out off the last ball of the innings.

Porterfield batted till the 39th over when he mistimed an on-drive off Sohail Khan and Shahid Afridi took a low diving catch running in from the edge of the circle.

Porterfield was the fifth Irish batsman to score a World Cup century after Jeremy Bray's 115 against Zimbabwe in 2007, Kevin O'Brien's 113 against England and Paul Stirling's 101 versus the Netherlands, both in 2011, and Joyce's 112 against Zimbabwe in this edition.

Pakistan had not won a match batting second in this tournament, but a run-rate of under five an over was easily achieved after a 120-run partnership for the first wicket between Sarfraz and Ahmed Shehzad (63).

The Irish bowlers were struggling to contain the runs when they secured two unexpected breaks with the wickets of Shehzad and Haris Sohail in the space of six runs.

Shehzad top-edged a pull off Stuart Thompson and was caught at mid-on by Joyce, while Haris was run out after Sarfraz refused a sharp single and turned his back on the non-striker.

Skipper Misbah-ul-Haq, who hit four half-centuries in the previous five matches, made 39 in a third-wicket stand of 82 with Sarfraz.

Pakistan made two changes from the side that upset South Africa, bringing in right-arm seamer Adil and Haris in place of the injured Irfan and senior pro Younis Khan.

The seven-foot tall Irfan was ruled out with a hip injury, but a bigger surprise was Pakistan's decision to omit the experienced Younis for this key game.

Ireland retained the same side that lost by eight wickets to defending champions India.