The UN spokesperson has reported earlier that 313,000 people have fled to neighboring Bangladesh in the last three weeks.
Almost 300,000 Rohingya Muslims have fled Myanmar into Bangladesh in last 15 days since new violence erupted and the U.S. is braced for a further surge, officials said, adding that it urgently need $77 million to assist the violence hit people in Rakhine state.
"We reiterate our condemnation of those attacks and ensuing violence", she said.
Myanmar, which has a Buddhist majority, denies citizenship to more than 1 million Rohingya, despite the group living in Rakhine state for generations.
The UN special rapporteur on human rights in Myanmar has said the latest violence may have left more than 1,000 dead, a lot of them Rohingya. Children and women flocked to every stopping vehicle, begging.
"Questions that are put to me suggest that many people have difficulty reconciling what appears to be happening to Muslims there with Myanmar's reputation as a Buddhist country", the Tibetan spiritual leader wrote in a letter to Suu Kyi shortly after the latest fighting broke out.
"We have received multiple reports and satellite imagery of security forces and local militia burning Rohingya villages, and consistent accounts of extrajudicial killings, including shooting fleeing civilians", Mr Zeid said.
Attacks by Arakan Rohingya Salvation Army (ARSA) militants on police posts and an army base on August 25 provoked a counter-offensive and a mass migration of villagers into the Cox's Bazar region of southern Bangladesh.
Noting that Myanmar had stripped Rohingyas of a wide range of rights, including citizenship, since 1962, the United Nations human rights chief took aim at official statements suggesting that refugees who had fled the violence would only be allowed back if they provide proof of nationality.
Basic resources were scarce, including food, clean water and medical aid. His wife, Ermine Erdogan, traveled to Bangladesh with a consignment of humanitarian aid last week, urging the government in Dhaka to keep its borders open for Rohingya refugees.
Aid agencies have been overwhelmed by the influx of Rohingya, many of whom are arriving hungry and traumatized after walking days through jungles or being packed into rickety wooden boats in search of safety in Bangladesh.
"It's a sign of the significant worry that Security Council members have about the situation that is continuing to deteriorate for the many Rohingyas who are seeking to flee Rakhine state", British Ambassador Matthew Rycroft told reporters.
Zeid urged the Myanmar government to "stop pretending that the Rohingyas are setting fire to their own homes and laying waste to their own villages", and called on authorities to allow his office access to investigate the situation.
The government had invited the Red Cross to assist them, he said.
"It is also driving up the risks that the country's five-year-old transition from military rule will stumble, that Rohingya communities will be radicalized, and that regional stability will be weakened", it said.