Top African cardinal in Vatican abruptly offers resignation - sources

FILE PHOTO: Cardinal Peter Turkson attends a news conference for the presentation of Pope Francis' new encyclical titled "Laudato Si (Be Praised), On the Care of Our Common Home", at the Vatican June 18, 2015. REUTERS/Max Rossi/File Photo

VATICAN CITY (Reuters) - Cardinal Peter Turkson, seen by some as a candidate to become the first African pope in about 1,500 years, has abruptly offered his resignation from a key Vatican department, sources familiar with the matter said on Saturday.

Turkson, 73, from Ghana, has been a key adviser to Pope Francis on issues such as climate change and social justice, and is the only African to head a Vatican department.