VATICAN CITY (AP) - Pope Francis has officially begun his ministry as the 266th pope, receiving the ring symbolising the papacy and a wool stole symbolising his role as shepherd of his 1.2-billion strong flock.

A cardinal intoned the rite of inauguration at the start of Tuesday's Mass, saying "the Good Shepherd charged Peter to feed his lambs and his sheep; today you succeed him as the bishop of this church."

Later a half-dozen cardinals approached the Argentine-born pope to vow their obedience.

The installation occurred in sun-drenched St. Peter's Square before tens of thousands of people, princes, sheiks, rabbis and presidents.