Almost 2,000 Christians gathered to peacefully prayer walk around a Planned Parenthood centre in Denver last Saturday.

Described as "truly a moment of grace, a moment of blessing" by Archbishop Samuel Aquila of Denver, the Eucharistic procession surrounded the facility with silent prayer for over an hour.

Planned Parenthood in Denver is the regional headquarters for Colorado and is responsible for almost half of the abortions carried out in the state, according to Ryan Walker, who helped to organise the event.

It was a "moment of praying to our Lord that hearts may be changed," Aquila told the Denver Catholic.

The procession was entirely peaceful. On the website advertising the march, it said: "No shouting or arguing. Only prayerful witness to the love and mercy of God."

Before the march began, the importance of silence was reiterated by Fr Scott Bailey, secretary to Archbishop Aquila.

"Silence is an essential part of the procession as we unite our voices with those who have been silenced by abortion," Bailey told the crowd.

The event was expected to attract between 500-800 people, but around three times that number turned up.

"This provided a bit of a challenge for us logistically, as 1,800 people don't exactly fit on the sidewalk of a city block," said Karna Swanson, communications director for the archdiocese.

"We wanted to make sure everyone who wanted to participate could, but we also didn't want to give any reason for the police department to shut the event down."

Despite the large numbers, the march went ahead peacefully.

"It was obvious to all that we were just there to pray," she said. "And pray we did, nearly everyone in the crowd was holding a rosary in their hands, and small groups throughout the crowd were praying the rosary together. We definitely stormed heaven with our prayers."