Arsenal have booked their spot in the last 16 of the FA Cup by comfortably seeing off fellow Premier League side Southampton 5-0 at St Mary's Stadium.

Both teams showed 10 changes apiece from last time out but it was the Gunners who eased their way to victory, secured thanks to two goals from Danny Welbeck and three from Theo Walcott on their respective returns from injury.

Welbeck bagged his first brace in this competition with less than a quarter of the game played, on what was his first start in 265 days, while Walcott - out for the past month - ensured that his side avenged their 4-0 thrashing here 13 months ago by adding three of his own in the remaining time.

There was a sign of things to come for the hosts pretty much from the off, as the lively Jeff Reine-Adelaide and Alex Oxlade-Chamberlain were both picked out in good positions inside the opening five minutes.

Neither player could make their shots count, but Welbeck had no such trouble soon after as he rounded off a 16-pass move by finding the net via the crossbar to put Arsenal ahead.

A second for the Englishman was not long coming, either, as he this time latched on to a ball over the top from Oxlade-Chamberlain and rather scuffed his shot under the body of Harry Lewis.

That finally sparked some sort of response from Southampton, who saw a Shane Long strike kept out by an otherwise untested David Ospina and Pierre-Emile Hojbjerg volley over the bar from a good position.

The Gunners may have taken their foot off the gas slightly but, moments after Shkodran Mustafi - the one survivor from last time out - glanced wide from close range, Walcott prodded the ball home after being picked out by two-goal Welbeck.

Ominously for the home side, Arsenal were quick to click into gear in the second half and they remained on top throughout, without troubling Lewis on too many occasions until the final quarter.

Hector Bellerin sent a shot down the middle for the youngster to keep out, but the next attempt did not arrive until 21 minutes from time when Walcott found a way through for his second of the evening.

It was a near-instant impact from Alexis Sanchez, who came off the bench and picked out his teammate to sweep the fourth of the match into the back of the net and signal the end of the contest for good.

There was still time for Walcott to register a hat-trick against his former club - his fifth for Arsenal - by getting on the end of a nicely-weighted pass from Sanchez to tuck past Lewis, who perhaps could have done better to keep it out.

Lucas Perez should have added a sixth in the final minutes, only to be denied by Lewis in this more one-sided repeat of the 2003 final between the two sides in Cardiff.

A sixth successive away win in this famous competition for the first time in Arsenal's history was never in doubt, as the Saints failed to find any sort of response to see their mini-resurgence come to a halt.