Portadown's Gary Hamilton in action against Viking FK

Arkins netted from the spot in stoppage-time time after Gary Hamilton had been pulled back.

It meant the Ports will be just 2-1 down going into the 28 July second leg.

Egil Ostenstad's 52nd-minute penalty gave Roy Hodgson's team the lead and then Finnish international winger Peter Kopteff made it 2-0 on 78 minutes.

David Miskelly was the first-half hero for the home side with two impressive saves to frustrate Viking.

The former Oldham goalkeeper produced a superb close-range block on seven minutes to parry a fine drive by the impressive Hannas Sigurdsson.

Miskelly was called into action again on 19 minutes to deny former Blackburn, Southampton and Rangers forward Ostenstad.

Portadown's resistance lasted until 52 minutes before a penalty was awarded after the Russian referee decided Ostenstad had been fouled inside a packed area.

The experienced striker made no mistake from the spot to push Viking in front.

Viking doubled their tally with a sublime finish by the lively Kopteff after neat footwork helped him to create space before a curling left-footed effort from long range left Miskelly stranded.

The game ended in dramatic fashion when Hamilton was brought down inside the area and Arkins stepped up to score and provide the Ports with a big boost before the trip to Norway.

Portadown manager Ronnie McFall said was proud of his players after their narrow defeat.

"I felt we entered the match in the best possible shape, given the lack of preparation time," said McFall.

"The players certainly put in maximum effort. When you look at the Viking team sheet they boast a host of international players.

"For us to finish the match just 2-1 down is a fantastic achievement."

Portadown: Miskelly, Craig, O'Hara, Clarke, Convery, Kelly, Marc McCann, Boyle, Gary Hamilton, Arkins, Neill. Subs: Murphy, Lindsay, Quinn, McAnallen, Teggart, Ryan Dickson, Baker.

Viking FK: Basso, Dahl, Deila, Hansen, Pereira, Kopteff, Hangeland, Nygaard, Gaarde, Ostenstad, Sigurdsson. Subs: Austbo, Gabrielsen, Berland, Sorli, Nkosinathi Nhleko, Mambo Mumba, Svenning.

Referee: Igor Zakharov (Russia)