Northern Rakhine has been nearly emptied of its Rohingya population since last August, when a military crackdown drove some 700,000 of the persecuted group across the border to Bangladesh.
The UN has accused Myanmar of waging an ethnic cleansing campaign against the Muslim minority, who face acute discrimination in the mainly Buddhist nation.
Myanmar denies the charge but has blocked UN investigators from investigating an area where thousands of Rohingya are believed to have been killed.
Since November Myanmar authorities have further demolished at least 55 villages with heavy machinery, clearing out all structures and vegetation, satellite images obtained by Human Rights Watch showed.
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At least two of the flattened villages were previously undamaged by fires, the watchdog said.
"Many of these villages were scenes of atrocities against Rohingya and should be preserved so that the experts appointed by the UN to document these abuses can properly evaluate the evidence to identify those responsible," said HRW's Asia director Brad Adams.
Myanmar's government spokesman could not be reached for comment.
Haunting images of levelled villages first circulated on social media earlier this month after they were posted by an EU diplomat.
At the time Myanmar's Social Welfare Minister Win Myat Aye told AFP the demolition was part of a plan to "build back" villages to a higher standard than before.
Myanmar has trumpeted a government effort to rebuild violence-gutted Rakhine and welcome back refugees under a repatriation agreement with Dhaka that was supposed to commence in January.
Analysts have also sounded the alarm over the government's rehabilitation projects, calling the sweeping destruction of villages, mosques and property only the latest move to erase the Rohingya's ties to their ancestral lands, and prevent them returning.
On Thursday UN agencies said they had struck a partnership with Myanmar and Japan governments to provide $20 million for humanitarian and development projects in Rakhine state, where authorities have restricted access for aid groups since the crisis.
Food and other assistance would be provided to "people of all communities in Rakhine state," the UN agencies said in a statement, adding that access had improved but remained restricted in some areas.
They have also been targeted by bouts of communal violence with ethnic Rakhine Buddhist neighbours and corralled into grim displacement camps in other parts of the state.
Myanmar's army says its August crackdown was a proportionate counterstrike against Rohingya rebels who attacked police posts in late August, killing around a dozen officials.
Many in the Buddhist majority revile the Rohingya and brand the group as foreign interlopers, despite their having lived in Rakhine for generations.