Tension is high in eastern Ukraine, where fighting between government troops and Russia-backed separatists has flared over the past three days.

The sides traded blame on January 31 for a surge in hostilities around the government-controlled town of Avdiyivka that has led to the highest casualty toll since mid-December.

The European Union called for "the fighting to stop immediately," saying it violated a cease-fire and put civilians at "grave risk."

The U.S. State Department issued a statement expressing deep concern about the renewed violence and calling for "an immediate, sustained cease-fire."

The UN Security Council said it would meet in closed session on January 31 to discuss the situation at Ukraine's request.

Kyiv also confirmed that the so-called Trilateral Contact Group (TCG), which includes Ukraine, Russia, and the Organization for Security and Cooperation in Europe (OSCE), will meet on February 1 in Minsk.

In addition, Kyiv has called for special session of the OSCE Permanent Council.

Ukrainian Deputy Prime Minister Ivanna Klympush-Tsintsadze announced on January 31 that seven Ukrainian soldiers had been killed and "dozens" wounded over the previous two days. Earlier, the Ukrainian military said 24 soldiers were wounded and that there were an unspecified number of civilian casualties.

Klympush-Tsintsadze claimed that the offensive was being directed by Moscow and urged the world to "know the truth about the crimes of the Kremlin."

"The Ukrainian fight against Russian invaders is a fight of freedom against tyranny, of the future against the past," Klypush-Tsintsadze said in a written statement.

Russia's Foreign Ministry issued a statement calling on Kyiv to cease "armed provocations" and observe the cease-fire agreements.

Russia's OSCE ambassador, Aleksandr Lukashevich, wrote on Twitter that Ukraine's call for an OSCE Permanent Council meeting was intended to provide "diplomatic cover" for "attacks" by the Ukrainian armed forces.

The U.S. mission to the OSCE issued a statement calling for the "combined Russian-separatist forces to recommit to the cease-fire to allow for repairs to critical infrastructure." The U.S. statement charged that "Russia and the separatists initiated the violence in [Avdiyivka]."

The United Nations secretary-general's spokesman, Stephane Dujarric, called on "all parties to immediately halt all hostilities" and "allow immediate and unhindered humanitarian access to the affected population."

Meanwhile, regional Governor Pavlo Zhebrivskyy said his office was working on a plan to evacuate thousands of civilians in Avdiyivka as shelling left many residents of the town north of Donetsk without electricity, water supplies, and heating in temperatures well below freezing.

But the AFP news agency quoted the town's military administrator, Fridon Vekua, as saying that no final decision to evacuate had been made.

"We see it as our very last resort because there is still a chance of restoring heating," he said.

The Russia-backed separatists said shelling caused casualties in the separatist-held provincial capital of Donetsk and damaged an electricity substation, cutting power to the Zasyadko coal mine and trapping more than 200 miners inside.

All of them were later evacuated, they said.

Ukrainian President Petro Poroshenko cut a visit to Germany short on January 30, citing what his spokesman called "an emergency situation verging on a humanitarian disaster" around Avdiyivka, which is home to a giant coking plant.

Kyiv and Moscow also accused each other of launching offensives in Avdiyivka and firing heavy artillery in defiance of a deal signed in Minsk in February 2015 that called for a cease-fire and steps to end the conflict between Kyiv and the Russia-backed separatists.

"The current escalation in Donbas is a clear indication of Russia's continued blatant disregard of its commitments under the Minsk agreements with a view of preventing the stabilization of the situation and achieving any progress in the security and humanitarian spheres," Ukraine's Foreign Ministry said in a statement.

Donbas is a name for the industrialized corner of eastern Ukraine where the separatists hold parts of the Donetsk and Luhansk regions.

EU foreign-policy chief Federica Mogherini called for the fighting to stop immediately, saying it would "allow for the urgent repair of critical infrastructures."

The intense fighting around Avdiyivka is a "blatant violation of the cease-fire" as stipulated by the Minsk agreements and puts civilian inhabitants at "grave risk," a statement issued by Mogherini's spokesperson said.

The chief monitor of the OSCE Special Monitoring Mission to Ukraine (SMM), Ertugrul Apakan, made a similar call, saying "violence on such a scale, involving the loss of life, is unacceptable."

Apakan also said in a statement that the SMM had reported on civilian casualties and observed damage to civilian homes and infrastructure.

They included the water-filtration plant in Yasynuvata, which it said thousands of people on both sides of the contact line depend for heating, electricity, and water.

A Western diplomat suggested that Moscow was behind the escalation in fighting, describing it as "Russia sending a message to the Ukrainians and (possibly) the new [U.S.] administration."

The increased fighting -- including "coordinated use of heavy artillery" -- came days after Russia warned in a TCG session that there could be an escalation if Ukrainian forces did not withdraw from positions near the water-treatment plant, according to the diplomat, who is involved in the process and spoke on condition of anonymity.

Kremlin spokesman Dmitry Peskov accused the Ukrainian government of conducting "aggressive actions" in an effort to undermine the stalled peace process and draw attention away from domestic problems.

The conflict in eastern Ukraine has killed more than 9,750 people since April 2014.

Despite substantial evidence, Russia denies claims by Kyiv, NATO, and Western governments that it stirred up separatism in the region and has sent troops and weapons to Ukraine to support the separatists.

The European Union, United States, and other states have imposed sanctions on Russia over the conflict, as well as for its annexation of Ukraine’s Crimean Peninsula in March 2014.

With reporting by Chistopher Miller in Kyiv, AP, UNIAN, Interfax, and TASS