The summer transfer window has now begun, with rumours and speculation continuing to swirl as Manchester City eye possible reinforcements.

The 2018-19 champions did not bring in a single player during the January transfer window, despite suffering a defensive shortage for much of the 2019-20 campaign, but they have already started their business for the summer.

Here, Sports Mole rounds up the latest news on possible comings and goings at the Etihad.

Monday morning's Manchester City transfer talk news roundup:

Manchester City offer Ilkay Gundogan in part-exchange for Saul Niguez?

Manchester City are allegedly prepared to lodge an approach for Atletico Madrid midfielder Saul Niguez.

Despite possessing a long-term contract and a £130m release clause, Saul is reportedly available for the right price during the summer transfer window.

However, while there has been previous interest from Manchester United, it appears that neighbours City are ready to make a bid for the versatile 25-year-old.

According to reports in Spain, City are willing to include Ilkay Gundogan in any proposal for the long-serving Atletico man.

Gundogan still holds a three-year deal at the Etihad Stadium, with the latest extension being penned just 12 months ago.

Nevertheless, it is claimed that Pep Guardiola is open to parting ways with a player who has contributed 22 goals from 164 appearances since his arrival from Borussia Dortmund in 2016.

Chelsea 'exploring possibility of signing Lionel Messi'

Chelsea are reportedly weighing up a potential move for Barcelona attacker Lionel Messi.

The Argentine is believed to be considering his future at Camp Nou, with various reports suggesting that the forward could seek pastures new during this summer's transfer window.

Manchester City and Inter Milan have both been strongly linked with the 33-year-old, who is said to have already informed new Barca boss Ronald Koeman that he could be on the move.

However, according to Sport, Chelsea are also exploring the possibility of signing the South American.

The report claims that the Blues have other areas that they want to address first, having already improved their attack by signing Hakim Ziyech and Timo Werner during this summer's transfer window.

Frank Lampard's side would allegedly be interested if Messi became available, though, and are keeping a close eye on developments as the speculation continues to gather pace.

Barca are said to be unprepared to sell their star player this summer for less than his £631m release clause.

More transfer news from Manchester City:

Barcelona 'ready to demand £631m for Lionel Messi'
Barcelona are allegedly prepared to demand that Lionel Messi's £631m release clause is paid in full if they are to sell the forward this summer. Read more.

Liverpool, Manchester City to battle for Wolves winger Adama Traore?
Liverpool and Manchester City are reportedly ready to battle it out in the race to sign Wolverhampton Wanderers winger Adama Traore. Read more.

Barcelona 'eye Paulo Dybala as Lionel Messi replacement'
Barcelona identify Juventus attacker Paulo Dybala as a potential replacement for Lionel Messi, according to a report. Read more.

Thomas Tuchel: 'Lionel Messi is very welcome at Paris Saint-Germain'
Paris Saint-Germain boss Thomas Tuchel says that Barcelona's Lionel Messi "is very welcome" at Paris Saint-Germain. Read more.

Napoli president: 'No suitable bids for Kalidou Koulibaly'
Napoli president Aurelio De Laurentiis insists that the Italian giants have still not received a suitable offer for Kalidou Koulibaly. Read more.