Fellow Dane Soren Hansen lost a three-stroke lead with bogeys on his last three holes, settling for a 71 after his shot hit the water on the 18th. Both are at 12-under 204.
Bjorn had six birdies, despite having played just once in the last seven weeks so he could spend time with his children.
Alastair Forsyth of Scotland shot a career-best 62, firing nine birdies, an eagle and a bogey, to finish a stroke behind the leaders. Lee Westwood (72) Simon Khan (69) and Richard Green (66) shared fourth place.
"I was just happy there wasn’t a cut after the opening day," said Forsyth, who began with a 76.
Bernhard Langer shot a 70, leaving him tied for seventh. John Daly took himself out of contention with a 76, labouring to five bogeys on his front nine.