All EU countries apart from Hungary agreed Thursday to ask the UN to appoint an expert to monitor the rights situation in Russia, diplomatic sources said.

Following weeks of intense discussions, 26 EU members agreed to draft a resolution urging the UN Human Rights Council to appoint a special rapporteur on Russia, two diplomats told AFP.

Luxembourg had agreed to take the lead and present the text to the council, one source said.

The decision comes amid concerns over an intensifying crackdown in Russia as its war rages in neighbouring Ukraine.

Speaking before the UN Human Rights Council on Monday, deputy UN rights chief Nada Al-Nashif denounced the "intimidation, restrictive measures and sanctions against people (in Russia) voicing opposition to the war in Ukraine".

These actions, she warned, "undermine the exercise of constitutionally guaranteed fundamental freedoms, including the rights to free assembly, expression and association".

Nashif, who is serving as acting High Commissioner for Human Rights until new chief Volker Turk replaces Michelle Bachelet, also decried "pressure against journalists, blocking of internet resources and other forms of censorship".

She said these were "incompatible with media pluralism and violate the right to access information".

On Wednesday, the UN Special rapporteur on the situation of human rights defenders around the world, Mary Lawlor, voiced alarm at the Kremlin's clampdown on activists.

She said Russia had been criminalising rights defenders for years, adding that it was "deeply alarming that the authorities have introduced even more new crimes that may be used against human rights defenders and create a suffocating effect on civil society."

"I urge the Russian authorities to immediately stop the crackdown on human rights defenders and repeal restrictive and discriminatory laws," she said.

Earlier this year, the council ordered a high-level probe of violations by Russian troops in Ukraine.

But there has been growing pressure for the body to also turn its gaze on rights abuses inside Russia.

Rights groups have long been urging EU countries to lead on a resolution, but the diplomatic discussions have dragged on amid fears of the implications if the resolution failed to obtain enough votes in the 47-member council.

Despite being kicked off the council earlier this year over its war in Ukraine, "Russia does not lack support," a European diplomat warned last week.

Now that a decision has been reached, rights advocates called for EU countries to swiftly present their draft text, which will be put to a vote during the last week of the current council session, which ends on October 7.

"It is incumbent upon European states to immediately table a resolution to establish the mandate or we risk another six months of inaction in responding to Russia's domestic human rights crisis," Dave Elseroad, of the Human Rights House Foundation, told AFP.