Protesters who have camped outside St. Paul's Cathedral in central London for six days have forced the venerable cathedral to close to visitors for the first time since World War II, church officials said Friday.

The Dean of St. Paul's, Rev. Graeme Knowles, said the decision to shut the doors of the iconic London church to visitors and tourists following the afternoon service was made with "heavy hearts" because of health and safety concerns.

He urged the protesters _ numbering roughly 500, according to organizers, allied with the "Occupy Wall Street" demonstrations _ to leave now that they have made their point.

"I'm asking the protesters to recognize the huge issues we face, asking them to leave the vicinity of the building so it can open as soon as possible," he told reporters.

Knowles said he recognizes the group's right to protest but wants them to recognize that the church also has "a right to open for our visitors."

The protesters, who have placed about 100 tents on church grounds, arrived last Saturday as part of a series of protests in many cities throughout the world in solidarity with the "Occupy Wall Street" activists in New York.

They have braved chilly weather with the help of donated food and blankets, said protester Ian Chamberlain, 27.

He said the group was in no hurry to leave despite the dean's plea.

"It's about deciding when it's no longer effective to be here," he said. "Many of us are determined to stay here as long as possible."

Protester Diane Richards, 36, said the cathedral closure was unnecessary because the impromptu camp has been safe and well organized.

"I'm really disappointed, because there has been no violence here," she said of the decision, which church officials had hinted at in recent days.

Knowles said health, safety and fire concerns _ notably the presence of flammable liquids and stoves set up by protesters _ were at the heart of the issue because the church has an obligation to keep visitors safe.

Earlier this week, the church said the "increased scale and nature" of the temporary camp could make it more difficult for the cathedral to stay open for worshippers and tourists.

The protesters have drawn a somewhat skeptical response from many Londoners who work in the nearby financial district known as the City.

"I have a sneaking suspicion they don't know what their message is," said lawyer Tom Day after reading some of the protesters' messages posted at the tent city.