Russia is under increasing pressure from world leaders to help stop the violence in Ukraine, where fighting intensified along the front line between government troops and pro-Russian rebels.

The U.S. and the European Union warned that Russia may face further repercussions after a rocket attack on the port city of Mariupol on Saturday. The projectiles were launched from rebel-held territory, the U.S., NATO, and the Organization for Security and Cooperation in Europe said. The separatists blamed government forces.

The battles erupting on the Sea of Azov coast indicate further escalation after fighting intensified this month, shattering a truce signed in September. The rise in violence sparked a flurry of diplomatic activity, with the U.S. and its allies putting pressure on Russia to use its influence on the rebels. The Kremlin denies military involvement.

“We are deeply concerned about the latest break in the cease-fire and the aggression these separatists” with Russian support are showing, U.S. President Barack Obama said at a news conference in New Delhi with Indian Prime Minister Narendra Modi. “We will continue to take the approach we have taken in the past, which is to ratchet up the pressure on Russia.”

Under Pressure

The threats to strengthen the economic pressure on Russia are destructive, President Vladimir Putin’s spokesman Dmitry Peskov was cited as saying by Interfax. Peskov reiterated that Russia isn’t a party to the conflict across its western border.

“We see attempts to derail the peace process,” Russian Foreign Minister Sergei Lavrov said Monday in Moscow. “We see repeated attempts by Kiev’s leadership to solve the problem by suppression of the southeast by force.”

The separatists are attacking along the entire front line, Ukrainian President Petro Poroshenko said at an emergency meeting of his security council in Kiev on Sunday. A government meeting led by Prime Minister Arseniy Yatsenyuk will discuss the situation in the Donbas region at 2 p.m. in the Ukrainian capital Monday.

Rebel Advance

Rebel forces need to push forward to prevent Ukrainian government troops from shelling the city of Horlivka, Interfax reported, citing self-proclaimed Donetsk People’s Republic leader Alexander Zakharchenko. The comments follow an about-face by Zakharchenko during the weekend, when he first declared than an offensive had started on Mariupol before saying the city won’t be stormed.

Seven government soldiers were killed and 24 wounded in the past day after clashing with separatists in eastern Ukraine, military spokesman Vladyslav Seleznyov told reporters Monday in Kiev.

Ukraine, the U.S. and its allies accuse Russia of supporting the rebels with hardware, cash and thousands of troops, accusations the Kremlin has repeatedly denied. Russia says the government in Kiev is waging war against its own citizens and discriminating against Russian speakers, who make up the majority of the populations of Donetsk and Luhansk.

Ukrainian Security Service head Valentyn Nalyvaychenko said Monday that an artillery unit that struck Mariupol was led by Russian officers and helped by Ukrainian spotters.

‘Unambiguous’ Escalation

The EU has no alternative but to impose tougher sanctions on Russia after the “unambiguous” escalation of fighting, Janusz Lewandowski, chief economic adviser to Polish Prime Minister Ewa Kopacz, said in an interview Monday on Polish Television’s First Channel.

German Chancellor Angela Merkel urged Russian President Vladimir Putin in a Sunday phone call to avoid further escalation in the conflict and to exert influence on the separatists to adhere to the cease-fire signed in September in Minsk, Belarus, according to an e-mailed statement from the Berlin government’s press office.

“There would be some very precisely targeted sanctions, but not general,” Latvian President Andris Berzins said in an interview in Riga, adding that the bloc will probably act this week by tightening penalties applied “to some individuals, to some Ukrainians involved from the separatists’ side, and some Russians.”

New Convoy

A new convoy of trucks carrying what Russia says is humanitarian aid will head for eastern Ukraine early on Jan. 27, RIA Novosti reported, citing the Emergencies Ministry in Moscow. Ukraine says such convoys cross the border illegally and it has accused Russia of using the trucks to send weapons and troops to the separatists.

Federica Mogherini, the EU’s top diplomat, called a meeting of the bloc’s foreign ministers for Jan. 29, her office said Sunday. U.K. Foreign Secretary Philip Hammond urged Russia to end support for the separatists.

The strategic port city of Mariupol suffered the deadliest attack yet as at least 30 civilians died and more than 100 were injured in the shelling Saturday, the Defense Ministry in Kiev said.

The death toll in the conflict, which has brought tensions between Russia and its Cold War-era foes to their highest pitch since the fall of communism a quarter century ago, rose to more than 5,000 since it began last April, according to the United Nations. Jan. 13-21 was “the most deadly period” in the conflict since the truce was signed, the UN said Friday.

Law Breach

The attacks on Mariupol “appear to have been launched indiscriminately into civilian areas, which would constitute a violation of international humanitarian law,” UN Secretary-General Ban Ki Moon’s office said in a statement dated Jan. 24.

Leonid Slutsky, a Russian lawmaker, said the shells were fired by the Ukrainian military as pretext to accuse the rebels of violating the truce, the state-owned news service Tass reported.

The situation along the front line is “stable” and Ukraine is reinforcing its positions, Defense Minister Stepan Poltorak said at the security council meeting.

Russia continues to send people and equipment across the border, Ukrainian military spokesman Andriy Lysenko told reporters in Kiev on Sunday.

The rebels are focusing their attacks on Debaltseve, near Donetsk, and are shelling government positions in the Luhansk region as well as around the Donetsk airport, the Defense Ministry in Kiev said. It reported “relative calm” in Mariupol.

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