UNITED NATIONS, April 16 -- The UN Security Council met in an open session once again on Wednesday to hear another grim report on the deteriorating conditions there, with Western ambassadors criticizing Russia's role and Moscow's envoy defending its actions.

It was the 12th such session of the 15-member UN body, Ivan Simonovic, the UN assistant secretary-general for human rights, reminded at the outset of his report.

"When I visited eastern Ukraine in March, the situation was already very tense," he said. "Meanwhile, the situation has significantly deteriorated."

He recalled recent reports of pro-Russian activists taking over Ukrainian government facilities in the east of the nation "using violence."

"Ongoing incidents and clashes between various groups of protesters, as well as with security forces, are of serious concern," he said. "While reports indicate that the number of protesters, including some allegedly from outside of the region, has not significantly increased -- we are speaking of a couple of thousand -- the level of violence and the proportion of armed protesters has."

"The situation in the east, if not adequately addressed as a matter of priority, risks seriously stabilizing the country as a whole," Simonovic said. "Those who exercise influence over the situation should take immediate action to halt the violence."

He called on all parties "to start an inclusive, sustained and meaningful national dialogue" in a process that should take into consideration the concerns of all those who live in Ukraine, including minorities, and address issues such as language rights and decentralization of the country.

The UN Human Right report, issued in Geneva on Tuesday, found that the March 16 referendum in Crimea to join the Russian federation was not fair.

"The report states that 'greatly exaggerated stories' and 'misinformed reports' were, 'systematically used to create a climate of fear and insecurity,' to support Russia's case for the annexation of Crimea," said Britain's Ambassador Mark Lyall Grant, citing the report. It raised "serious concern about violations of civil and political rights of in habitants of Crimea."

It contained damning evidence that "Russia used propaganda and misinformation to exacerbate tensions and to destabilize," he said. "We remind Russia that it cannot use the situation in Ukraine, for which it bears significant responsibility, as a pretext for further illegal military activity."

Representatives of the European Union, Russia, Ukraine and the United States meet to discuss the situation in Ukraine in Geneva on Thursday.

Defending its stance, Moscow says the present Ukrainian government is illegal as Kiev sees the Crimea referendum to join Russia as illegal.

"The High Commissioner on Human Rights (HCHR) report of (Tuesday) is biased" against Russia and pro-Russians in Ukraine, said Russia's UN Ambassador Vitaly Churkin.

"Ukrainians must launch a dialogue insuring that it is comprehensive and full-fledged in nature," he said. "All, without any exception, regions and political forces in the country must participate in it on an equal basis with equal rights in resolving pressing issues."

"All of this must be reflected in a deeply-reformed constitution, one which would be seen by the multi-ethnic Ukrainian society as a sound one to serve as a long term basis for a legal government," Churkin said.

"Without this it will be very difficult for Ukraine to preserve its unity and to resolve pressing issues on extricating itself from this crisis," he said.

For his part, Liu Jieyi, the Chinese permanent representative to the United Nations, told the Security Council that "China is deeply concerned about the escalation of the situation in Ukraine."

Liu stressed that the priority now is to work within the framework of law and order, resolve differences through dialogue and negotiation, and fully accommodate the legitimate rights, interests and concerns of all regions and ethnic communities.

"This is the only approach that can bring lasting peace and stability to Ukraine in keeping with the long-term and fundamental interests of the nation as a whole and all its communities," he said.

Meanwhile, Nigerian UN Ambassador Joy Ogwu, whose country serves as rotating council president this month, took her turn after all the other ambassadors to speak in her national capacity.

"We are encouraged by the relentless and consistent engagement of the UN in Ukraine," she said. "Indeed, we believe in the central role of the United Nations in de-escalating tensions in Ukraine."

The UN provides an impartial platform as well as professional expertise, she said.

"We urge all concerned parties to cease beating the drums of war," Ogwu said.

"They must work assiduously towards de-escalating tensions and embrace dialogue in all its ramifications in the larger interests of the people of Ukraine," she said.