Ngog joined from Liverpool on a three-year deal for an undisclosed fee while Kakuta joins the Wanderers on loan.

Cahill had been widely tipped to leave the Trotters with Spurs boss Harry Redknapp working hard to secure his signature. But a failure to reach an agreement means Cahill will stay put.

Coyle was delighted with the signing of the 22-year-old Frenchman Ngog, who scored 19 goals in his time at Anfield after joining Liverpool from Paris St Germain in 2008.

Coyle told Bolton's official website www.bwfc.co.uk: "David will be a great addition to our squad. He is quick, he can score goals and he knows what the Barclays Premier League is all about.

"Added to that there is his European experience with Liverpool in the Champions and Europa Leagues. He has represented his country at a host of junior levels and he will offer our team further attacking options.

"We are delighted to bring another quality young prospect to Bolton."

Meanwhile, Chelsea winger Kakuta has signed on a six-month loan deal after failing to establish a regular first team place at Stamford Bridge. Kakuta spent part of last season on loan to Fulham.

Coyle added: "I'm delighted that Chelsea have enabled us to take Gael on loan and I'd like to thank Andre and the club for that.

"He is someone whose progress we have tracked since he first broke into the Chelsea first team a couple of years ago. He is skilful, quick, exciting to watch and I'm really looking forward to working with him."

Ngog and Kakuta bring the total of signings made by Coyle in the summer transfer window to eight, after previously landing Darren Pratley, Nigel Reo-Coker, Chris Eagles, Tyrone Mears, Tuncay and Dedryck Boyata.