The speaker of parliament, Oleksandr Turchynov, told lawmakers “a large number of terrorists” were “liquidated” in an industrial area at Severodonetsk in the Luhansk region this morning. The anti-rebel operation around the city of Slovyansk, about 80 kilometers (50 miles) to the west, is “in an active offensive phase” involving “very active exchanges of fire,” Interior Minister Arsen Avakov said on Facebook.

At least 12 deaths were reported in Luhansk yesterday after about 500 insurgents attacked the border-guard headquarters. Five rebels died in that assault, the border guards said, and a blast in the center of the city killed seven people, according to the local health service. Rebels initially said it was an air strike, which the government denied.

The violence underscored the tension with Russia as President Barack Obama arrived in Poland at the start of a European tour, during which he’ll meet leaders including Ukrainian President-elect Petro Poroshenko to discuss the crisis. The U.S. and the European Union say Russia, which annexed Crimea from Ukraine in March, is behind the unrest in Luhansk and nearby regions.

Obama will cross paths with Russian President Vladimir Putin later in the week in Paris and during 70th-anniversary commemorations of the World War II allied landings in northern France.

Russia’s Micex stock index declined 0.6 percent at 1:30 p.m. in Moscow following a 2.3 percent gain yesterday to its highest level in three months, after Russia gave Ukraine an extra week to pay in advance for gas supplies before risking a cutoff that could also lead to shortages in Europe.

Russian Energy Minister Alexander Novak said talks with Ukraine in Brussels yesterday in their dispute over gas prices, brokered by the EU, were “constructive.”

Still, a shutdown in supplies is “still on the agenda,” Ukrainian Prime Minister Arseniy Yatsenyuk told lawmakers in Kiev. Talks between Russian gas exporter OAO Gazprom and NAK Naftogaz Ukrainy, Ukraine’s state-run gas company, were continuing today in Berlin, he said.

Ukraine carries about 15 percent of the natural gas used by Europe through its Soviet-era pipelines and accuses Russia of using energy as a political weapon by ramping up prices.

A total of 181 people have been killed since unrest broke out in eastern Ukraine, Prosecutor General Oleh Makhnitsky said in Kiev. The death toll includes 59 servicemen. Another 293 people have been wounded and 220 kidnapped, he said.

Obama announced a $1 billion fund today to help boost defensive capabilities of European allies shaken by the crisis. The president will officially call on Congress to approve the fund this afternoon at a joint news conference in Warsaw with Polish President Bronislaw Komorowski.

NATO defense ministers were set to discuss the Ukraine crisis during two days of talks in Brussels that start today.

“There are still tens of thousands of Russian troops along the Ukrainian borders and that massive troop presence is not justified,” the alliance’s secretary general, Anders Fogh Rasmussen, told reporters before the talks. He called on Russia to “de-escalate the situation, first and foremost by a full withdrawal.”

Meanwhile, Ukrainian Justice Minister Pavlo Petrenko proposed confiscating Russian companies’ assets in Ukraine and abroad to compensate for losses of about $92 billion resulting from the annexation of Crimea, Russia’s Kommersant newspaper reported. It said Petrenko made the comments in Kiev.

Obama’s trip offers a series of venues for possible talks on the Ukraine conflict. He’ll meet other Group of Seven leaders in Brussels starting tomorrow, though they won’t decide on further steps to sanction Russia during the talks, according to a German official speaking to reporters today on condition of anonymity.

The U.S. president will also attend a dinner with Francois Hollande June 5, the same day the French president hosts Putin, before they travel on to the D-Day commemorations in Normandy on June 6.

U.S. Vice President Joe Biden will travel to Ukraine for Poroshenko’s inauguration on June 7, the White House said yesterday.