But Stuart Pearce's men were then pushed onto the back foot by their opponents, with Moussa Konate's late equaliser denying them victory.
The hosts pushed forward frantically in search of a winner but they came no nearer than a Marvin Sordell effort that crashed against the bar.
And the greatest damage could yet be felt in the dressing room, with both Bellamy and Joe Allen needing to be checked after sustaining worrying knocks.
Great Britain struck first when Ryan Giggs sent over a cross from the right, for which Micah Richards challenged.
It was Steven Caulker who got his head to it, though, nodding it down for Bellamy, whose first-time finish flashed past Ousmane Mane and into the far corner.
Sadio Mane chipped disappointingly wide for Senegal before Ibrahima Ba's shot required a smart low save from Jack Butland.
In the second half, Zargo Toure thundered a shot over before Saliou Ciss brought another decent save out of Butland.
Allen's exit after an hour was another cause for concern as he had already been down once, and then Bellamy was brought down on the edge of the area.
Bellamy was able to continue, although he was eventually replaced.
Great Britain looked to be heading for victory until Konate struck eight minutes from time, delicately lifting the ball over an advancing Butland.
Meanwhile, Oscar played a starring role as Brazil were forced to fend off a brave fightback from Egypt to secure a 3-2 win at the Millennium Stadium.
The midfielder set up Rafael and Leandro Damiao for the first two Brazil goals, before Neymar made it 3-0 at half-time in front of a crowd of 26,812.
The South Americans took their foot off the gas after the break and were punished as Mohamed Aboutrika and Mohamed Salah pulled goals back for Egypt, but it was not enough for the Africans in this Group C clash.