Middlesbrough have completed the signing Portsmouth’s 22-year-old Nigerian striker Aiyegbeni Yakubu for £6m.

Yakubu is not eligible to join the Teesside club until the next transfer window opens in June.

Boro have also moved to secure Stewart Downing’s position at the club by opening negotiations about improving the 4-year contract signed by the 20-year-old England winger last year.

“Negotiations are just starting now and there’s a long way to go,” said Downing.”I’ve got a lot to think about and obviously big decisions to make about my future.

“Negotiations have started now and obviously if things are right on the playing side and off the field I’ve got no problem in being here.”