Detectives investigating the murder of a Saudi Arabian student are questioning a 19-year-old man who was initially arrested over a separate attack.
Nahid Almanea died after she was stabbed 16 times while walking along a path in Colchester, Essex, on Tuesday morning.
The 31-year-old had been taking an English language course at the University of Essex since January as part of her studies for a life sciences PhD.
Essex Police said the man was arrested shortly after midnight in connection with a separate assault. His arrest followed a report from a woman that while she was jogging near Peache Road, Colchester, at around 10pm, on June 19, a man had approached her and tried to grab her.
She was able to fight him off and made her way home and then immediately contacted police.
A police spokesman said: "Following further enquiries he was then further arrested shortly after 4pm today in connection with the murder investigation.
"He remains in custody for questioning."
The police statement comes amid fears a serial attacker may be responsible for the killing. Police have said their are "obvious similarities" between Ms Almanea's death and that of James Attfield, a vulnerable man with brain damage who died after being stabbed more than 100 times in a park in Colchester in March.
Officers said there are many possible motives, including the fact Ms Almanea was wearing full Muslim dress.