British Open officials have changed the way the bunkers are raked at the Royal Liverpool course after complaints from players that they were overly "penal".

Masters champion Jon Rahm described Royal Liverpool's 82 bunkers as "proper penalty structures" after having to play backwards out of one during his opening 74 on Thursday, while Rory McIlroy needed two shots to escape a greenside trap on the 18th.

Four-time major winner McIlroy said: "When you hit it into these bunkers you're sort of riding your luck at that point and hoping it's not up against one of those revetted faces."

Two-time US PGA winner Justin Thomas had a nightmare on the final hole at Hoylake after finding a bunker, ending up with a quadruple-bogey nine.

In response, the R&A instructed greenkeeping staff to build up the edges of the bunkers to allow more balls to roll back into the centre.

"Yesterday afternoon the bunkers dried out more than we have seen in recent weeks and that led to more balls running straight up against the face than we would normally expect," the R&A said in a statement.

"We have therefore raked all of the bunkers slightly differently to take the sand up one revet on the face of the bunkers.

"We routinely rake bunkers flat at most Open venues but decided this adjustment was appropriate in light of the drier conditions which arose yesterday.

"We will continue to monitor this closely for the remainder of the championship."

Even those players who managed to successfully escape from the bunkers on day one had expressed their concerns, with former champion Stewart Cink speaking out following a bogey-free 68.

"Eventually it'll catch up with you," the 2009 winner said. "The bottoms of them are so flat that if a ball comes in with any momentum, it's just going right up to the lip and stop.

"There's not a little upslope that helps you at all. They are very penal."