Yvonne Ridley had been reporting from Pakistan
Yvonne Ridley had been reporting for the Sunday Express and Daily Express from Peshawar and Islamabad in Pakistan.
A spokesperson for the Daily Express said the 43-year-old was the paper's chief reporter and a highly experienced journalist who had covered several conflicts in many countries around the world.
Sunday Express Editor, Martin Townsend, said: "She is an experienced and courageous journalist."
Sunday Sun Deputy Editor, Colin Patterson, said: "She is a very warm, gregarious person who is very determined and tenacious."
Ms Ridley also worked for the News of the World, the Daily Mirror, The Sunday Times, The Observer and the Independent before joining Express Newspapers two years ago.
Her eight-year-old daughter, Daisy, has made her own appeal for her mother's safe return.
"I just want mummy to come home, " Daisy said.
"She's a very kind person and she wouldn't do anything wrong."
Ms Ridley met Daisy's father, a former Palestine Liberation Organisation Colonel, in Cyprus while working on an assignment for the Sunday Sun.
Daoud Zaaroura, 54, who is chief executive of the Northern England Refugee Service, described his former wife as "a journalist of great integrity and courage who shows no fear in pursuit of a story".
"She often feels she can simply cruise through any given situation," he added.
After the Lockerbie disaster nine years ago, Ms Ridley got the first interview with Ahmed Jibril, the head of the Popular Front for the Liberation of Palestine, which had been among the chief suspects.
But a former colleague of Ms Ridley told BBC News Online she was not known for taking unnecessary risks.
"She was very knowledgeable, well travelled, had been around the world and was as tenacious as most journalists are.
"She was not the sort of person to take risks but was as hungry as most journalists are to get stories."