Former England Under-21 defender Mawson turned home Renato Sanches' 52nd-minute corner to put the visitors ahead before substitute Ayew rifled in late on to settle an uninspiring contest at a sparsely-populated Madejski Stadium.

With Reading aiming to win promotion to the Premier League and Swansea hoping to stay there, both managers made multiple changes for the third-round tie.

The Swans' seven alterations included a first start since returning to the club for striker Wilfried Bony, while Royals boss Jaap Stam opted to freshen up his starting XI by bringing in nine new faces.

It was the hosts who had the better of the early play and Romania forward Adrian Popa should have done better when he blazed over from the edge of the box, before midfielder John Swift fired straight at Swansea's Swedish goalkeeper Kristoffer Nordfeldt.

Swansea, who have been a top-flight club since a 4-2 victory over the Royals in the 2011 Championship play-off final, gradually eased their way into the game and threatened twice in quick succession through Luciano Narsingh.

The Dutch winger had the ball in the back of the net with his first attempt - only to be penalised for a foul on Jordan Obita - before being denied by the legs of Royals keeper Anssi Jaakkola after racing towards goal two minutes later.

Bayern Munich loanee Sanches was one of the players retained by Clement from the weekend draw at Tottenham and the Portugal midfielder was perhaps a little too keen to impress as he twice shot woefully off target from distance in a dour first half.

The clubs had drawn their previous meeting 0-0 on Boxing Day 2012 and extra-time felt like a realistic prospect when referee Andy Davies called time on the opening period.

The half-time whistle sparked ugly scenes on the pitch as an altercation involving Ivory Coast international Bony resulted in a large brawl, although players from both sides disappeared down the tunnel without a card being shown.

Bony began to have more of a positive impact following the restart and, after he saw an effort blocked behind, the visitors broke the deadlock from the resulting right-wing corner.

Sanches took the set-piece, delivering low to the near post where former Barnsley centre-back Mawson casually swept the ball into the far corner with the aid of a deflection.

Swansea lifted this trophy back in 2013 and their passage to the next round was sealed with seven minutes remaining.

Ghana international forward Ayew, a 62nd-minute replacement for Wayne Routledge, broke towards goal before cutting inside and producing an emphatic finish into the bottom right corner.