Jennifer Lopez and Marc Anthony renewed their wedding vows in Las Vegas on Sunday morning.

The couple, who were married over four years ago, did the deed at 3.15am in the Forum Tower Penthouse at Caesar's Palace. They'd spent the earlier part of the evening dining privately with Bradley Ogden and at the tables and were also spotted at Pure Nightclub.

"They were both winning at the craps table and Marc kept saying that it was going to be a lucky night," a source told People magazine.

The service, officiated by Reverend Steven Smith, was reportedly unplanned.

"It was totally a spur of the moment thing," another source said.

"They decided around 12:30 in the morning that they wanted to do it and started calling for ministers."

The couple were joined in a joint ceremony by their friends, baseball player Carlos Beltran and his wife Jessica.

According to a witness: "Carlos gave his wife a specially engraved ring and gave Marc and Jennifer special rings as gifts. Carlos and Jessica renewed their vows first, then Jennifer and Marc went."

The impromptu ceremony took place in the rotunda of the newly-renovated Penthouse.

"Initially, they were supposed to do the ceremony outside on the suite’s balcony but it was too cold, so they had to move it inside. That was the only thing that didn't go according to plan," the source told People.

But that didn't deter the couples who were witnessed by 12 people.

"Marc actually said the suite was so beautiful that it deserved its own zip code. He thought it was perfect."

Lopez also looked "beautiful" in a black dress, the source added.

The couples celebrated their renewed vows with a bottle of Dom Perignon champagne.

The ceremony rounded off a busy Vegas weekend for Lopez and Anthony. On Friday the couple watched 'Believe', illusionist Criss Angel's new show for Cirque Du Soleil befored heading out to LAX Nightclub and The Bank.