Maria Golovnina, 34, was rushed to hospital in the Pakistani capital but doctors were unable to save her, Reuters said in a statement.
Before taking up her role in Islamabad in 2013, Golovnina, who was a Russian national, had worked in postings around the world, including in London, Singapore, Moscow, Afghanistan and Iraq.
Reuters editor-in-chief Stephen Adler said the whole agency mourned Golovnina’s death.
“She was one of our finest journalists, combining fearlessness with an upbeat enthusiasm that inspired confidence, respect and affection from everyone around her. She will be deeply missed,” he said in a statement.
Police said a post-mortem examination would be needed to establish the cause of death but there was no initial indication of foul play.
According to her Twitter account, she posted last tweet on February 18.
— Maria Golovnina (@MariaGolovnina) February 18, 2015