Fast bowlers Martin Bicknell and Kabir Ali have been called up by England for the fourth Test against South Africa at Headingley, the England and Wales Cricket Board said on Monday.

The duo were added to the squad as possible replacements for Steve Harmison, who is suffering from a calf injury and could be ruled out of the Test which starts on Thursday. The series is balanced at 1-1 after England won the third Test on Monday.

"The indications given to me are that there are serious doubts about the way (Harmison) was moving around here," chairman of selectors David Graveney was quoted as saying on the BBC web site.

He said 48 hours was "not a very long time to recover from that sort of injury".

Despite struggling with the injury, the Durham bowler claimed the wicket of Herschelle Gibbs during the Trent Bridge Test, which England won to level the five-match series.

The 34-year-old Bicknell played two Tests for England 10 years ago against Australia while Worcestershire-based Ali, 22, was included in England's one-day squad earlier this season but did not get a game.

"He has been one of the more unluckiest guys not to have been selected (before)," Graveney said referring to Bicknell.

"He's a very experienced performer and we do have a very young attack."

Squad: Michael Vaughan (capt), Kabir Ali, James Anderson, Martin Bicknell, Mark Butcher, Andrew Flintoff, Ashley Giles, Stephen Harmison, Nasser Hussain, James Kirtley, Ed Smith, Alec Stewart (wicketkeeper), Marcus Trescothick.