Radcliffe has had a poor start to her Olympic year

Radcliffe had been included by Great Britain for both the 8km and 4km races at the event in Brussels.

The European champion has recently suffered a virus but was expected to run over both distances.

Radcliffe had been hoping to bounce back to form after losing a 10km race in Puerto Rico last month.

But on Thursday she said: "I went for my usual long run on Sunday morning and everything was okay.

PAULA RADCLIFFE FACTFILE Born: Northwich, Cheshire DOB: 17 Dec 1973 1992: World junior cross-country champion 1997: 4th in World Championship 5,000m 1999: World Championship 10,000m silver 2000: 4th Olympic 10,000m 2001: World cross-country champion 2002: London Marathon winner, European 10,000m champion, Commonwealth 10,000m champion, Sports Personality of the Year, world record at Chicago Marathon 2003: Breaks world record at London Marathon

"Then in the evening I went for a light run and felt a stiffening in my hamstring and knew I needed treatment."

Radcliffe underwent treatment at UK Athletics' high-performance centre in Loughborough but failed to rectify the problem.

"I found it impossible to run uphill and in a cross-country race there will always be plenty of them," she said.

"Now it's case of getting back into training. That should be shortly as it isn't a serious injury."

Radcliffe's progress over the last year has been blighted by illness and injuries.

She missed the world championships last summer with a leg injury, suffered a virus last November and struggled with a cold in last month's race in Puerto Rico, where she was outsprinted by Lornah Kiplagat.