ASAN, South Korea (Reuters Life!) - The founder of the Unification Church, Sun Myung Moon, held his first mass wedding ceremony in years on Wednesday, blessing 20,000 people from around the world at a college he founded.

Moon, who founded the church officially called the Family Federation for World Peace and Unification, and his wife were on hand for the mass ceremony, where 1,000 couples took their wedding vows and another 18,000 renewed their vows.

"As men and women representing the 6 billion mankind, go out and become the builders of the world of peace and ideals," Moon told the couples gathered on the sprawling grounds of the Sun Moon University, about 100 km (60 miles) from Seoul.

Moon and his wife sprinkled holy water over a dozen select couples called onto the stage and declared them tied in wedlock. He declared in 1992 that he and his wife were messiahs.

One of Moon's sons, Hyung Jin, has taken over the day-to-day running of the church with an estimated 5 to 7 million followers around the world, and had told Reuters in an interview in December he would keep mass weddings to a more manageable scale -- in the hundreds.

The Unification Church considers the Korean peninsula sacred.

Its website (www.unification.org/index.html) said Jesus Christ appeared to founder and overall leader Sun Myung Moon as he was praying and asked him "to complete the task of establishing God's kingdom on Earth."

Critics have vilified the group as a heretical, weird and dangerous cult, questioning its murky finances and how it indoctrinates followers.

(Reporting by Christine Kim and Reuters TV; writing by Jack Kim; Editing by Sugita Katyal)