Arbour is scheduled to meet with President Hamid Karzai, parliamentarians, and members of the judiciary. She will reportedly also meet with NGO officials and people who say they have suffered human-rights violations.
Arbour's visit comes shortly after the release of a report by Amnesty International on November 12 claiming that Afghanistan's intelligence service has tortured detainees. Amnesty urged NATO-led coalition forces in Afghanistan not to turn over prisoners to Afghan authorities.
The rights watchdog said Afghanistan's National Directorate of Security (NDS) is a "serious threat to those in its custody."
A spokesman for the NDS, Sayeed Ansari, on November 13 denied the charges, and said Afghanistan has always followed Afghan and international law in its treatment of prisoners, RFE/RL's Radio Free Afghanistan reported.
"We have observed human rights. Human rights representatives recently visited all the prisons and detention centers of the National Directorate of Security, and they met with the prisoners," Ansari said. "We reject the [Amnesty International] report. They can come and once again visit our prisons, and see the situation and that there is no problem."
A NATO official also denied the allegations, saying that the transfer of prisoners from NATO-led troops to Afghan forces "was developed with the Red Cross/Crescent and meets international standards."
Arbour previously visited Afghanistan in 2005. She is also to meet with the Afghan Independent Human Rights Commission during her visit.
(with material from agency reports)