Use play icon at top of page to watch BBC One coverage of Plymouth v Leeds or audio icons to listen to BBC radio commentaries from all three ties
FT: Plymouth Argyle 1-4 Leeds United - Gnonto breaks deadlock; Galloway levels before Summerville, Rutter & a Hardie OG in extra time
Leeds will face Chelsea or Aston Villa in fifth round
FT: Coventry City 4-1 Sheffield Wednesday - Palmer opens scoring, Cadamarteri levels before O'Hare & Wright set up home tie against sixth-tier Maidstone
FT: Southampton 3-0 Watford - Mara scores twice & Adams adds third to secure Saints a trip to Liverpool
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Southampton 3-0 Watford
Southampton's unbeaten run extends to 24 games in all competitions. After a poor first half, the Saints dominated the second half, with two goals from Sekou Mara and one from Che Adams.
It's Premier League leaders Liverpool at Anfield next for Russell Martin's side on Wednesday, 28 February in round five.
Southampton 3-0 Watford
Seventeen-year-old Sam Amo-Ameyaw, who has represented England Under-18s, nearly gets his first Saints senior goal but his strike hits the top of the right upright.
Plymouth 1-1 Leeds
Extra time it is!
Plymouth 1-1 Leeds
And now Ryan Hardie almost wins it for Plymouth but his strike is pushed behind for a corner.
Plymouth 1-1 Leeds
Matthew Upson
Former England defender on BBC One
It is now a very attacking looking midfield now for Leeds.
Coventry 4-1 Sheffield Wednesday
Kasey Palmer got the first goal of the match, before the visitors equalised seven minutes later through Bailey Cadamarteri.
But the hosts ran clear in the second half with two goals from Callum O'Hare plus one from Haji Wright to set up a home match against National League South side Maidstone United in round five on Monday, 26 February.
Plymouth 1-1 Leeds
Joe Gelhardt is so close to snatching the win for Leeds but his effort strike the woodwork!
Plymouth 1-1 Leeds
Galloway equalises for Plymouth
Is this the goal that will take this game to extra time?
Plymouth 1-1 Leeds
The Leeds fans are in great voice, despite the prospect of having to deal with the conditions for another 30 minutes.
We're into four minutes of time added on, with Crysencio Summerville on now as well for Leeds, replacing Sam Byram.
Plymouth 1-1 Leeds
Extra-time is looming as we enter the final minute of normal time.
Conditions are really brutal now with the wind and rain seeming to get heavier and heavier.
Plymouth 1-1 Leeds
Matthew Upson
Former England defender on BBC One
I've got a feeling at this point that it's going to come down to will and who wants it most. That's where we're up to now in this FA Cup tie.
Southampton 3-0 Watford
Saints substitute Samuel Edozie collects the pass from Will Smallbone and only has back-up goalkeeper Ben Hamer to beat.
Edozie fools the keeper by giving him the eyes, Hamer dives the wrong way but the ball smashes off the left upright.
Southampton 3-0 Watford
Sekou Mara has almost grabbed his hat-trick. Two goals in the bag and he curls just over with a great effort.
Coventry 4-1 Sheffield Wednesday
It has been a tough second half for 18-year-old keeper Pierce Charles in only his second senior appearance for the Owls.
He has conceded three, although was not to blame for any of them. Coventry have another effort and Victor Torp lets fly, but just wide of the post.
Plymouth 1-1 Leeds
Gnonto puts Leeds 1-0 up at Plymouth
This was the Leeds opener that looked like it might be enough to send them through before Plymouth's equaliser out of nothing.
Coventry 4-1 Sheffield Wednesday
It should be five for Coventry. Sub Ellis Simms gets the ball and he is central, 15 yards out and unmarked but can only send his finish over the top. It won't matter as Coventry are going through, but he should've done better.
Plymouth 1-1 Leeds
The Plymouth fans are bouncing now as Leeds send on Patrick Bamford and Georginio Rutter for Mateo Joseph and Jaidon Anthony.
Plymouth 1-1 Leeds
Matthew Upson
Former England defender on BBC One
We thought the conditions may play a part in the outcome this evening and I think we've just seen that happen.
Che Adams
That will do it. Che Adams has set up two and scored the third.
Joe Rothwell curls in a free-kick, the Watford defenders are sleeping and Adams is there to get a foot on to it to guide it into the net.
Liverpool v Southampton in round five at Anfield. A great day for the Saints fans to look forward to.
Adams puts Southampton 3-0 up
Brendan Galloway (78 mins)
Game on!
Brendan Galloway gets the equaliser although I'm not sure how much he knew about it.
Plymouth send a free-kick into the box and it is knocked back across the face of goal by Ashley Phillips, the ball diverting into the back of the net off Galloway's chest.
Galloway equalises for Plymouth