UN special rapporteur on human rights Yanghee Lee has been denied access to some areas in Myanmar's northern Rakhine State, with the government citing "security concerns" for its decision.

Al Jazeera also learned on Sunday that Lee was only allowed to speak to individuals who were preapproved by the government while she visited Muslim Rohingya villages in the area.

"These are things that will certainly hamper her investigation," Al Jazeera's Florence Looi, reporting from Sittwe, said. "Lack of access will make her job more difficult."

As part of her 12-day visit to Myanmar, Lee is spending three days in Rakhine - home to around 1.2 million stateless Rohingya, a Muslim minority that has suffered decades of poverty and repression, and been denied basic rights, such as citizenship and freedom of movement.

READ MORE: Global leaders warn Aung San Suu Kyi over Rohingya

Lee also visited the border guard posts, attacked in October, as well as a prison.

Northern Rakhine has been under strict military lockdown since October 9, when a gang killed nine border police officials near the border with Bangladesh, leading to a clampdown that has left anywhere between 84 and 400 Rohingya dead.

According to the UN, at least 65,000 Rohingya have reportedly fled across the border to Bangladesh to escape violence allegedly committed by the military, including the burning of homes, rape and murder of civilians.

The Myanmar government and military have denied all the allegations.

On Friday, Lee met Muslim community leaders during her visit to a Rohingya neighbourhood in Sittwe.

Lee also visited border guard posts, the attacks on which in early October triggered clearance operations by the military.

But a powerful ethnic party rejected a request for a meeting with Lee on Friday evening.

"We are not meeting her because we don't believe she and her organisation [the UN] have a will to resolve the issues fairly," Ba Swe, joint secretary of the Arakan National Party, told Anadolu Agency on Saturday.

"The issues will never be solved as long as they accept these Bengalis as members of this country's ethnic groups," Ba Swe said, using a term that suggests Rohingya are illegal immigrants from neighbouring Bangladesh.

International pressure

The crisis in Myanmar has put Aung San Suu Kyi's administration under international pressure, with rights watchdog Human Rights Watch criticising the government of the Nobel Peace Prize laureate for failing to hold the country's military accountable for the crackdown on Rohingya.

Lee continues her travels through the conflict zone on Sunday before returning to Yangon later in the week.

Al Jazeera's Looi also said the UN envoy will also look into reports that the flow of aid to the Rohingya has been "severely curtailed" since the military operation began three months ago.

"The UN said they are concerned about the rising rate of malnutrition among the Rohingya in this area, because this is an area where food security is already in doubt," Looi said, adding that as many as 150,000 people are dependent on aid.

Across the border in Bangladesh, Al Jazeera's Maher Sattar, who is reporting from Cox's Bazar, said Rohingya refugees have also corroborated reports of abuse.

"We've come across people, who have been shot. We've come across children. Every single person here, they are quite unanimous in their stories of villages being burned and relatives being killed."

A law passed in Myanmar in 1982 denies Rohingya - many of whom have lived in Myanmar for generations - citizenship, making them stateless.

The law denies Rohingya rights to Myanmar nationality, removes their freedom of movement, access to education and services, and allows arbitrary confiscation of property.

Rohingya have fled Myanmar in droves for decades, with a new wave of migrations occurring since mid-2012 after communal violence broke out.

Because of their lack of citizenship, they are also considered as refugees in Bangladesh, and many of them are confined in refugee camps for decades.