SYDNEY (REUTERS) - New Zealand rugby star and United Nations Children's Fund (Unicef) ambassador Sonny Bill Williams has provoked a storm of controversy after posting graphic photos of dead children following a visit to a Syrian refugee camp.

A World Cup-winning All Black, he travelled to the camp in Lebanon's Bekaa Valley earlier this month with Unicef to highlight the plight of the 1.2 million refugees fleeing the conflict in Syria.

"What did these children do to deserve this?," Williams tweeted late on Tuesday with pictures showing the bodies of two young children with horrific injuries. "This summer share a thought for the innocent lives lost everyday in war."

The publication of the images drew a critical reaction from several followers and local media.

"Sorry you (feel) the need to post pictures of dead bodies to highlight your cause. Where's your respect?" one person responded.

"Wow that's heavy, but do spare a thought for your young followers who will not understand this," said another.

Many comments, however, were supportive of Williams'decision to post the images.

"I'm glad you posted this, you created discussion and I applaud you for your humanity in visiting these victims."

A spokesman for Unicef Australia said while she understood the motivation of Williams to share the pictures, the organisation did not support the publication of such images.

The powerful and talented Williams has been a divisive sporting figure Down Under after switching clubs and codes and interspersing his rugby with professional boxing fights.

He won wide praise during the Rugby World Cup in England this year after first offering tickets to the semi-final to Syrian refugees and then giving his winner's medal away to a young fan who was tackled by a security guard after the match.