Senior cardinals from around the world have defended Pope Francis against a spate of recent attacks from conservatives challenging his authority.

In an unusual move, nine cardinals in a group advising the Pontiff on Vatican economic and structural reforms issued a statement expressing "full support for the pope's work" and guaranteeing "full backing for him and his teachings".

The statement was unusual in that the cardinals - from Italy, Chile, Austria, India, Germany, Congo, the United States, Australia and Honduras - customarily issue statements only at the end of their meetings, which are held four times a year.

The statement said the cardinals expressed their solidarity with the pope "in light of recent events," which Vatican sources said was a clear reference to the attacks.

 On 4 February, mystery activists working under cover of dark plastered posters around Rome criticising the pope for moves seen as targeting conservatives in Church.

They featured a picture of a stern-faced pontiff and the slogan: "Where's your mercy?" The posters accused Francis of several controversial acts, including what they called "the decapitation of the Knights of Malta."

This was a reference to an ancient Catholic order of knights which is now a worldwide charity. Its former grand master, or top leader, handed in his resignation after he and his main backer, American Cardinal Raymond Leo Burke, lost a battle with the Vatican for control of the order.

Last week, a fake electronic edition of the Vatican daily newspaper, L'Osservatore Romano, was sent anonymously to Vatican officials and journalists.

It poked fun at the pope for not having responded to a rare public challenge in November by four conservative cardinals, led by Burke, who accused him of sowing confusion on important moral issues such as homosexuality and divorce.