Manchester City's Sergio Aguero believes on a good day his side can beat anyone but insists they must focus on beating Schalke to avoid another shock result in the Champions League. (2:56)

Manchester City are the subject of a fourth investigation into alleged financial wrongdoing, with the Premier League joining FIFA, UEFA and the Football Association in probing their transfer dealings.

The Premier League's investigation relates to the signing of academy players and third party ownership.

"The Premier League has previously contacted Manchester City to request information regarding recent allegations and is in ongoing dialogue with the club," a statement read.

"The league has detailed financial regulations and strong rules in the areas of Academy player recruitment and third-party ownership.

"We are currently investigating these matters and will allow Manchester City every opportunity to explain the context and detail surrounding them."

Reports of City breaching FFP rules emerged following allegations made by German publication Der Spiegel, with leaked documents purportedly obtained by Football Leaks.

A UEFA statement published on Thursday had confirmed European football's governing body was launching an investigation into the Premier League champions for an alleged breach of FFP rules, as City stand accused of manipulating money earned from a sponsorship deal with Etihad airways.

City said they "welcome the opportunity to the opening of a formal UEFA investigation as an opportunity to bring to an end the speculation," following the announcement.

Meanwhile, manager Pep Guardiola, who won the Premier League last season and defended his Carabao Cup title in February, said he has no concerns his achievements at City would be tainted by the allegations

"No, absolutely not," he said.

If found guilty, City could face a possible Champions League ban.

City were found guilty of breaching FFP rules in 2014, and received a £49 million fine from UEFA as well as seeing their Champions League squad reduced for the following campaign.

The FA are investigating a payment allegedly made to former player Jadon Sancho, when he was signed from Watford in 2015.

FIFA's investigation centres around the signing of eight players under the age of 18 from outside Britain.