Pompey moved to within four points of the League One automatic promotion places after recording a 2-0 win over Scunthorpe at Fratton Park.
Second-half strikes from Omar Bogle and Jamal Lowe ensured the Blues closed the gap on second-placed Barnsley - who were held to a goalless draw at Doncaster on Friday night.
On-loan forward Bogle's smart turn and finish handed Kenny Jackett's men the all important breakthrough 19 minutes from time, before Lowe's fine finish made sure of the win after 87 minutes.
Although Pompey remain fourth despite the triumph, they sit two points off place-above Sunderland - after they overcame Walsall - while the gap to the stuttering Tykes and the top two is just four with eight games to play.
The blustery conditions made things difficult for both sides, but the Blues should have gone ahead after 26 minutes.
Birmingham loanee Viv Solomon-Otabor's pass slid Lowe in behind.
The winger beat the offside trap before rounding the onrushing Jak Alnwick, but Iron skipper Rory McArdle recovered superbly to block the Pompey man's effort.
It was the hosts who looked the more likely to break the deadlock, spurning another great opening two minutes before the break.
The ball fell to the feet of Bogle just inside the area, although his effort was parried away by Alnwick.
Brett Pitman reacted quickest to put the ball back across goal on the rebound, only for Lowe to slip with the goal gaping, seeing his scuffed attempt go just wide.
Pompey were seeing plenty of the ball after the restart yet appeared short of ideas of finding a way through Scunny, who were content on sitting in.
Jackett's troops were in the ascendancy, pushing for the breakthrough and Lowe was once again denied 23 minutes from time.
Scunthorpe failed to clear a cross, with substitute Gareth Evans poking back into a dangerous area.
Lowe reacted quickest to pick up the loose ball but Alnwick was out to smother the winger's attempt.
The Blues' patient probing was finally rewarded as they went in front four minutes later.
Evans's free-kick was fired into a dangerous area and front man Bogle pounced, taking the ball from Ben Close, to fire home first time on the spin from the edge of the area.
Winger Lowe then got in on the act, getting in behind before firing a thunderbolt past Alnwick to make sure of the victory.