The images of dead children tweeted by Sonny Bill Williams are purportedly casualties of a Russian airstrike on a Syrian school.
Without picking sides, Williams wrote: "What did these children do to deserve this? This summer share a thought for the innocent lives lost everyday in war."
The death of the children has been blamed on Russian airstrikes against forces opposing the Syrian government in the country's multi-sided civil war. The photographs were used on Turkish news site Takvim on Boxing Day with a story quoting a Syrian civil defence official saying the children were killed during a bombing attack in the Idlib province.
The official, Mahmoud Dagim, said five children had been killed when Russian jets bombed Zikar school in the Jarjanas region. Four others were also said to have been killed.
The area is under the control of forces opposing the Syrian government, but not aligned with the terror group Isis (Islamic State).
While Russia has said its attacks are aimed at Isis forces, there have been claims it is using the opportunity to attack forces opposing the Syrian regime, of which it is supportive. Some of those opposition groups have won support from the US and Turkey in the fight against Isis.
The photographs appear to have first been posted online by a Syrian man Seraj Aborass, who used his Twitter feed to blame Russian planes for a "massacre". A string of casualty images purportedly from the bombing, including those posted online by Williams, were tweeted by an "activist media" Twitter account linked to government opposition forces.