By Philip Pullella
VATICAN CITY (Reuters) - Pope Francis joined an inter-faith day of prayer on Thursday to call on God to end the coronavirus pandemic, brushing aside criticism from ultra-conservative Catholic groups, with one accusing him of associating with "infidels".
A multi-faith committee formed after the pope's historic visit to the Arabian Peninsula last year came up with the proposal that Christians, Muslims and Jews pray, fast and perform charitable works on Thursday.
"Maybe there will be someone who will say 'This is religious relativism and it cannot be done," Francis said in the homily of his morning Mass at the Vatican on Thursday.
"But how can we not pray to the father of us all? Each one prays as they know how, as they are able to. We are not praying one against the other, one tradition against another ... (but) as brothers," he said.
The nine-member Higher Committee on Human Fraternity, which is based in Abu Dhabi, promotes dialogue among religions. It comprises Muslims, Jews and Christians, including a Vatican cardinal and one of the pope's private secretaries, who is an Egyptian priest.
In Thursday's initiative, the Committee expressed support for medicine and scientific research but also invited people to pray "according to the teachings of their religion," as well as to fast and do works of charity to ask God to end the pandemic.
Not all Catholics heeded the appeal.
In a series of tweets, the traditionalist Catholic blog Rorate Caeli mocked the pope. One tweet called the inter-religious prayer day "Francis' Fast with Infidels".
Rorate Caeli accompanied its tweets with pictures of sumptuously laid tables overflowing with food, suggesting that Catholics should feast, not fast, on Thursday.
One was accompanied by a picture of a roasted piglet. Observant Muslims and Jews do not eat pork.
Another influential traditionalist group, The Society of Saint Pius X, called the pope's promotion of the prayer day the "poison fruit" of the Catholic Church's dialogue with Islam.
The traditionalists, a vociferous minority in the 1.3 billion-strong Roman Catholic Church, have consistently criticised the pope since his election in 2013, particularly over his overtures to the Muslim world and his call for a Church that stresses mercy over doctrinal rigidity.
They have also opposed his support of agreements to limit global warming.
Despite their tweets, reaction to the committee's appeal among Catholics - as well as among Jews, Muslims and other Christian denominations - was mostly positive, with the hashtags #HumanFraternity and #PrayTogether going viral on Twitter.
The Church of Jesus Christ of Latter-Day Saints, commonly known as Mormons, tweeted: "Our hearts are joined with our brothers and sisters in the Muslim, Catholic and other faith traditions".
In his own tweet, Francis said: "May God have mercy on us and put an end to this tragedy, this pandemic, as well as the pandemics of hunger, war, and children without an education. This we ask as brothers and sisters, everyone together."
(Reporting By Philip Pullella; Editing by Gareth Jones)