Pope Francis has urged Catholics in China to be "united to the rock" of the church in Rome.

Francis made the comments Wednesday during his general audience ahead of an important feast day May 24 for Chinese Catholics at the shrine of Sheshan in Shanghai.

He said: "We too will ask Mary to help Catholics in China to be always credible witnesses of this merciful love among their fellow citizens and to live spiritually united to the rock of Peter upon whom the Church is built."

China severed relations with the Holy See in 1951 when the Communists took over. Worship is officially allowed only in state-authorized churches outside the pope's authority. In 2007, Pope Benedict XVI sent a letter to Chinese faithful urging them to unite under his authority.