Police officers are patrolling churches and mosques in London to provide reassurance in the wake of Pope Benedict's comments about Islam.
Some people argued with protesters outside Westminster Cathedral
Catholic and Anglican churches, as well as Muslim mosques were visited by local police units this weekend.
Police are investigating a Muslim protest at Westminster Cathedral over reported comments by one activist.
The row began last week, when Pope Benedict XVI repeated criticism of the Prophet Muhammad by a medieval scholar.
He said he was "deeply sorry" his speech had offended Muslims, saying the medieval text he quoted, which said the Prophet Muhammad had brought the world only evil, did not express his personal opinion.
But there has been a mixed response from Muslims across the world, some leaders accepted it, others said it was not enough.
It is thought attacks on churches in Palestinian areas, and the killing of a nun in Somalia, may have been linked to the row.
A Scotland Yard spokeswoman said patrols in London would continue as part of "reassurance policing by the safer neighbourhood teams".
No specific intelligence is believed to have been received about possible attacks at religious buildings.
A spokesman for the Roman Catholic Archdiocese of Southwark said officers had called in to some of its churches on Sunday.
He added: "My understanding is this was done on the police's own initiative, their own risk assessment."
There were no arrests at the protest outside the Roman Catholic Westminster Cathedral on Sunday, attended by about 100 people.
But there have been about 25 complaints about the event - thought to be related to reported comments made by one activist.
Assistant Commissioner Tariq Ghaffur said they would investigate the protest and "other publicly made statements" to find out if any crime had been committed.
"We will always proportionately police all protests but equally will take decisive action where crime is committed."