"We are deeply concerned about the intimidation and sometimes prosecution of individuals in Saudi Arabia for exercising their right to freedom of expression," Ravina Shamdasani, a spokeswoman for the U.N. High Commissioner for Human Rights, said in a statement.
The rights commission said its concern was sparked by the four-year prison term and lashing given Omar bin Mohammed al-Saeed for defaming the Saudi monarchy and for making remarks deemed offensive on his personal Twitter account.
Shamdasani said it "appeared" Saeed was targeted for his work on civil and political rights in Saudi Arabia. Several of his associates have been detained on similar grounds, she said.
Saudi Arabia has been criticized regularly for its human rights record, though Saudi King Abdullah in February swore in 30 women to serve on Shura Council -- the Consultative Assembly of Saudi Arabia -- for the first time in the country's history.
Women councilors have a special seating area and designated entrances and exits to comply with a no-touch policy with male counterparts.