During his stay, lasting through April 26, Hammarberg is set to meet with Foreign Minister Sergei Lavrov and other senior Russian officials.
The commissioner will also pay a four-day visit to the North Caucasus region, including Chechnya and nearby regions Daghestan and Ingushetia, to study the human rights situation.
The co-rapporteurs on Russia at PACE, Luc Van den Brande and Theodoros Pangalos, are also expected to pay a visit on April 20-23 to oversee Russia's implementation of its commitments to the Council of Europe.
Alleged human rights violations by security forces in Chechnya and other parts of Russia's North Caucasus, including reported torture and executions, have come under harsh criticism from the Council of Europe.
Earlier this month, a PACE committee released an 'introductory memorandum' calling the situation in the region "by far the most alarming" in all 47 Council of Europe member states, Amnesty International and Human Rights Watch said.
The text issued by Dick Marty, PACE's Legal Affairs and Human Rights Committee rapporteur on the North Caucasus, "highlighted ongoing human rights violations by security forces, including enforced disappearances, torture, and extrajudicial executions," the rights groups said.
Although the active phase of the Kremlin-led antiterrorism campaign against Chechen separatists officially ended in 2001, periodic bombings and clashes between gunmen and federal troops still disrupt Chechnya and nearby regions.
