Gabriel Martinelli scored a hat-trick as Arsenal came from behind to beat Portsmouth comfortably at Fratton Park and progress to the FA Cup fourth round.

After FA Cup shocks involving Wrexham and Macclesfield earlier this weekend, it looked as if the Gunners, who made 10 changes to their starting line-up, could be on the end of another when Colby Bishop put the Championship hosts ahead after three minutes.

But Arsenal were only behind for five minutes before Christian Norgaard forced the ball in via Portsmouth's Andre Dozzell after a trademark Gunners corner to level.

That goal settled the visitors down and they took the lead from another set-piece when Martinelli flicked Noni Madueke's corner into the net after 25 minutes.

Maduke had a chance to add a third from the penalty spot after he was brought down by Zak Swanson but the England international dragged the ball wide.

Martinelli, who also hit the post and missed a good chance in the first half, added a third after Gabriel Jesus played a low cross into the area following some quick thinking by Myles Lewis-Skelly and the Brazilian tapped in from close range.

Martinelli grabbed his third from another Arsenal corner when the forward flicked the ball on from the near post and into the net.

There was then a piece of history when at 16 years and 135 days defender Marli Salmon became the youngest player to feature for the Gunners in the FA Cup.

It has been a mixed season for Martinelli - who was heavily criticised for an altercation with injured Liverpool defender Conor Bradley during the week.

But the winger will hope his first hat-trick for the Gunners will be the boost he needs, as Arsenal attempt to win major silverware for the first time since their 2020 FA Cup success.

Martinelli has lost his place as a regular starter in the Premier League but has excelled in the Champions League, scoring five goals in his five appearances in the competition.

The fight for places has gone up a notch this season, with more depth in the squad after eight summer signings - including forwards Madueke, Eberechi Eze and Viktor Gyokeres.

That depth allowed Arteta to make 10 changes and still name a team featuring Spain international Mikel Merino, plus England internationals Madueke and Eze.

Key centre back Gabriel Magalhaes was the only player to keep his place from the draw against Liverpool on Thursday.

Merino, captain for the day, was one of Arsenal's best performers at Fratton Park. Again asked to play in an unfamiliar deep-lying midfield role, the 29-year-old used his experience to do an important job.

Alongside the positives of the win, the hat-trick for Martinelli and minutes for squad players, Arteta was able to welcome back Kai Havertz as the forward featured for the first time since picking up a knee injury on the opening day of the season.

This was the first of four away games in four different competitions for the Gunners - and it is a sign of how successful their season has been so far that they still have so much to play for.

Arsenal take on Chelsea in the Carabao Cup semi-final first leg on Wednesday. Portsmouth's next game is on Saturday against Sheffield Wednesday in the Championship.