A bicycle-riding robber suspected of being behind at least one of four similar attacks was arrested after he stole $300 from a woman at knifepoint in Yuen Long yesterday, police said. The 53-year-old allegedly stopped a cyclist in Castle Peak Road, outside Wong Uk Tsuen at 6.30am and threatened her with a knife. A 48-year-old villager chased the man, who was arrested. On March 25, a 65-year-old woman was robbed of $2,600 in the village in similar circumstances. On April 12 and 13, three other robberies were committed by a cyclist, thought to be in his 20s or 30s.