A US woman found bound and stabbed to death near Jerusalem worked for a UK-based Christian organisation that promotes Christianity among Jews.
Israeli police are investigating whether the killing was political but have not ruled out a criminal motive.
Kristine Luken's travelling companion, who survived the attack, told police the pair had been set upon by two Arab men while hiking near Jerusalem.
No suspects have been detained, and no group has claimed responsibility.
The survivor, Kaye Susan Wilson, told police that she and Ms Luken - initially identified by police as Christine Logan - were attacked on Saturday while walking in the Mata forest, near the town of Beit Shemesh.
Ms Luken's body was found on Sunday.
Ms Wilson, a British native and naturalised Israeli, said the two men accosted them and suddenly attacked them with what appeared to be a butter knife.
"One of them took out a very long knife," Ms Wilson said. "I played dead. I saw [the knife] hadn't gone into my heart. My friend was dying, I heard her making gurgling sounds."
Ms Wilson said she played dead and managed to flee the scene and reach the road, where people put her in contact with police.
She was then taken to hospital in Jerusalem, where she was said to be in a stable condition.
As she received treatment police and border officials mounted a large-scale hunt for her friend, fanning out through the forested areas around Beit Shemesh.
Searches were also carried out near the Green Line that divides Israel from the West Bank, the Haaretz newspaper reported, as fears grew that the missing woman had been kidnapped.
Speaking to Haaretz, police spokesman Micky Rosenfeld said: "She did not know who they were, or what the reason for the attack was. We are examining whether this is a nationalistic stabbing, but other leads are being examined as well."
Initially, Israeli police described Ms Luken as a British citizen.
Ms Luken was attached to CMJ UK, a British organisation that says it aims to persuade Jews to accept Jesus as the Messiah.
In a statement, CMJ described Ms Luken as "a committed Christian with a deep love for the Jewish people" she had met.
"It is a tragedy that such a lively, caring and faith filled person should have been struck down in such a way," the group wrote. "We are praying for her friends and family at this tragic time."