Key points:

- Pope Benedict XVI to resign on 28 February
- Pope, 85, said he no longer has the strength to continue in office
- Conclave to elect a new Pope before end of March
- Benedict first pontiff to resign in nearly 600 years
- Vatican says Pope took aides by "surprise"
- Elected on 19 April 2005 when he was 78
- In Pictures: Pope Benedict XVI