The signings will severely weaken United ahead of their QTS League Cup final against Celtic next month and the Tannadice club failed in an initial bid to tempt Hibernian to sell former Terrors midfielder Scott Allan.

Celtic have also been linked with a move for Kilmarnock’s Scotland Under-19 forward Robbie Muirhead and they look set to tie up a move for Derry City forward Michael Duffy, who has held talks at Celtic Park.

Hamilton are set for a huge financial boost after accepting a £1m-plus bid from Norwich for top goalscorer Tony Andreu.

An Accies statement read: “The club can confirm that a bid has been received for Tony Andreu from Norwich City. After discussions with the player and Norwich in respect of their offer, and in line with our ethos of development, the bid has been accepted subject to medical.”

Accies are reported to have failed in a bid to sign Dean Shiels from Rangers as a replacement but they earlier snapped up 21-year-old Czech midfielder Nico Sumsky following his departure from Slovakian club Dukla Bystrica. Sumsky, who has nine Czech youth caps, trained with Accies last week.

Aberdeen earlier made an ambitious move by snapping up midfielder Kenny McLean from St Mirren.

The Dons appeared to trigger a release clause in the 23-year-old’s St Mirren contract to purchase the midfielder for a six-figure fee.

Aberdeen, who loaned striker Declan McManus back to Morton, have secured the former Scotland Under-21 midfielder on a three-and-a-half-year contract.

St Mirren replaced McLean by signing 18-year-old attacking midfielder Emmanuel Sonupe from Tottenham on loan until the end of the season.

It is understood that Partick Thistle are set to sign Lyle Taylor on loan from Scunthorpe following his successful spell at Firhill in the second half of last season, when he netted seven goals. The Jags released another striker, Nathan Eccleston, to pave the way for the deal.

Motherwell manager Ian Baraclough signed England Under-21 goalkeeper George Long from Sheffield United and is in the running to sign several more players from the Sky Bet Football League.

The 21-year old 6ft 4in custodian has played 80 times for the Blades first team.

Long, who had a loan spell at Oxford United last year, said: “I’m really looking forward to it and it’s a new challenge for me to play in Scotland.

“It will be great to get back playing and hopefully help push the team up the table.

“I’ve heard a lot of good things about the club and the manager so I can’t wait to get started.”

Dundee had a busy day, signing striker Paul Heffernan from Hibernian and making Stephen McGinn’s loan move from Sheffield United a permanent transfer.

Dundee also signed teenage defender Ben Priest from Wolves, although he is not viewed as an immediate first-team player, while sending out Phil Roberts and Dylan Carreiro on loan. Roberts has signed for Alloa while Carreiro has rejoined Arbroath.

St Johnstone released 32-year-old midfielder Gary McDonald, who has made 17 appearances this season, while Ross County released Dutch midfielder Darren Maatsen.

Rangers are set to sign several players on loan from Newcastle.

22-year-old attacking midfielder Haris Vuckic is reportedly on his way to Ibrox.

The Slovenian, whose sole international cap came in a 1-1 friendly draw against Scotland in 2012, has made 18 appearances for Newcastle and also had loan spells with Rotherham and Cardiff. He arrived at St James’ Park six years ago.

Swiss teenage defender Kevin Mbabu could also be loaned from the Magpies.