The 27-year Senegal international has agreed a four-year deal with the Black Cats after spending four seasons at the Reebok Stadium.

Diouf becomes Keane's fifth signing of the summer following the arrivals of Teemu Tainio, Nick Colgan, David Meyler and Pascal Chimbonda.

Keane was eager to bolster his attacking options ahead of the start of the Premier League season and the versatile Diouf is able to play on the wing or as a deep lying forward.

Diouf began his career with Sochaux and then had spells at Rennes and Lens before a £10million switch to Liverpool after impressing at the 2002 World Cup.

After a bright start at Anfield he struggled to live up to expectations and was sent on loan to Bolton in 2004, before a permanent switch to Wanderers -where he has since rejuvenated his career.

Diouf's time in English football has not been short of controversy and the most high-profile incident was when he spat at a Celtic fan in a UEFA Cup tie while at Liverpool.

But despite his controversial past Keane has no qualms about signing a player he believes other clubs "love to hate" if he can improve the quality in his squad.

"El-Hadji is a great signing for us and we're thrilled to get him," Keane said.

"He has bags of Premier League and international experience, which is exactly what we have been targeting this summer.

"El-Hadji has always been the kind of player opposition teams and supporters love to hate, a thorn in the side, and that's why we're delighted to now have him in our squad.

"Our coach, Ricky Sbragia, has also worked very closely with him and speaks extremely highly of him, so we're looking forward to working with El-Hadji, I think he's a signing that will excite our supporters."

Meanwhile Chimbonda has revealed that Keane's ambitious plans for the club are part of the reason he has been able to lure players of the calibre of Diouf and himself to Wearside.

"I know Sunderland have a good manager and when I came here I saw the training ground and I think it's a good place for me," he told www.safc.com.

"It's a good challenge for me and I hope this season will be good.

"Sunderland have good players and the aim is to stay in the Premier League, but I know the manager wants to progress, play football, and win games - hopefully that will happen.

"It didn't come as a surprise to me (to move here) because apart from Manchester United, Arsenal, Chelsea and Liverpool, every club is the same, nobody is bigger."

After securing the signature of Diouf, Keane will now turn his attentions to the pursuit of Tottenham duo Younes Kaboul and Steed Malbranque.

While there has been little development on a deal for Malbranque, a move for Kaboul seems likely after Portsmouth manager Harry Redknapp - who was also interested in signing the Morocco-born Frenchman - admitted the Black Cats were the favourites to land the player.

"I still want to bring in Kaboul but he has spoken with Sunderland," Redknapp told The News.

"I know Aston Villa also want him but Roy Keane has met him now too. I'd say we are third now behind the other two teams."