The Myanmar authorities have accused Muslim Rohingya militants of killing 28 Hindu villagers whose bodies were allegedly found in a mass grave.
The army says the bodies of 20 women and eight men and boys were found in two pits in northern Rakhine state.
The state has been in turmoil since 25 August when Rohingya militants launched deadly attacks on police posts.
Over 400,000 Rohingya have since fled an offensive by the military, which the UN accuses of ethnic cleansing.
Hindus as well as members of the majority Buddhist population in Myanmar (also called Burma) have also been displaced from their homes by the violence in Rakhine.
The military denies widespread reports it has committed atrocities, saying it only targeted those belonging to the militant Arakan Rohingya Salvation Army (Arsa) which launched the attacks.
On Monday, the Myanmar government's Information Committee said in a Facebook post, accompanied with a graphic photo, that the mass Hindu grave had been found near the village of Yebawkya in Rakhine.
It said 300 Arsa militants had rounded up about 100 villagers and killed most of them on 25 August, the same date as the start of the latest phase of the conflict, in claims attributed to an unnamed Yebawkya villager.
The claims could not be independently verified. Authorities have restricted journalists and independent observers from freely travelling in Rakhine state, citing security concerns.
But a BBC reporter has spoken to Hindus who fled from Rakhine to Bangladesh and said they were threatened and attacked by Arsa. They also said some Hindus had been killed and some houses burned by the militants.
Hindu villagers in the Yebawkya area told the AFP news agency that Rohingya militants attacked their communities on 25 August, killing many and taking others into the forest.
The Hindus have said they were attacked by Arsa because the militants suspected they were government spies.
Arsa has consistently denied such accusations, and on Monday a spokesman told Reuters news agency that claims of its militants killing villagers were "lies".
Buddhists are the majority in Rakhine state but there are also Hindu and Muslim communities as well as the Rohingya.
The Rohingya - a stateless mostly Muslim minority - are widely despised in Myanmar, where they are considered to be illegal migrants from Bangladesh, despite the fact that some have been in Myanmar for generations. Bangladesh, which now hosts about 800,000 Rohingya, also denies them citizenship.
Inside Rakhine, bitter ethnic tensions have led to waves of communal violence in the past.
Myanmar's military says its operation is aimed at rooting out Rohingya militants and has repeatedly denied targeting civilians. But many of those who fled to Bangladesh accuse the military and Buddhist mobs of beating and killing villagers and razing their communities.
Earlier this month the UN special rapporteur on human rights in Myanmar, Yanghee Lee, said more than 1,000 people may have been killed in the conflict, most of them Rohingya.
The army says some 400 people have been killed during military operations, the vast majority of them Arsa militants. But BBC correspondents say it is very likely that many of them were civilians.
Thousands of young men joined the attacks in support of Arsa, armed with machetes and bamboo sticks, but very few were trained and armed militants, they say.