The protesters wearing lavender stoles, the symbol of the movement for women's ordination, unfurled banners reading "Born to be priests" and "Vocation is important, not gender" in the illegal protest.
Three police officers, two in a golf cart and one on foot, stopped the protest, the fourth such action according to Erin Hanna, head of the US-based Women's Ordination Conference, admitting that they had no permit.
"If women don't do it, no one will," Colette Joyce of London, an activist from a group of would-be women priests called New Wine, told AFP, saying she was "terrified" of the reaction in her parish when she returned home.
The women timed the protest to coincide with the final days of the Vatican's Year for Priests.
After what German activist Angelika Fromm called "a disappointing Year for Priests and a disastrous year for the Roman Catholic Church," she called on Pope Benedict XVI to "leave his ivory tower and to face the urgent demands of today's life."
It was among several references to the paedophile priest scandals that have returned to engulf the Catholic Church since last November, a new wave after large-scale scandals hit the Church in the United States in 2002.
"The absolute hypocrisy of the Year for Priests celebration cuts to the core of what is wrong with the (Church) hierarchy today," Hanna told the news conference.
"The Vatican is all too happy to turn a blind eye when men in its ranks destroy the lives of children and families, but jumps at the chance to excommunicate women who are doing good works," she said.
"While the hierarchy spends their time covering up scandals and throwing major celebrations for themselves, Catholic women are... making a positive difference in the world," she added.
Mary Ann Schoettly of the eastern US state of New Jersey is among more than 100 women who have been ordained by woman bishops who were in turn consecrated by one or more male bishops whose identities will remain secret until their deaths.
"Reclaiming our ancient spiritual heritage, women priests are shaping a more inclusive, Christ-centred Church of equals in the 21st century," said Schoettly, wearing a traditional Catholic priest's collar.
"We are here to stay. We are not going away," she warned.
SIC: AFP