More than 7,500 people including senior military officials have been detained and nearly 9,000 officials sacked from their posts in the crackdown following the attempt to overthrow President Recep Tayyip Erdogan on Friday.
"The constitutional order needs to be fully preserved in accordance with the principles of democracy and fundamental rights, including through the full respect of freedom of speech and assembly and adherence to due process," UN spokesman Farhan Haq said.
UN Secretary-General Ban Ki-moon had called on Friday for a quick and peaceful return to civilian rule in Turkey.
"The United Nations continues to stand firmly by Turkey and its democracy during this difficult moment," Haq said.
The United Nations reaffirmed its opposition to capital punishment, saying countries that have abolished it should not reverse course.
Erdogan yesterday said he would consider reinstating the death penalty, abolished in Turkey since 2004.