ODESSA/SLAVYANSK, Ukraine — The last two days have seen the worst violence in Ukraine since the February uprising.
More than 50 people have died, most in a horrific inferno on Friday in the southern city of Odessa. Forty-two pro-Russian protesters were incinerated when the fire engulfed a trade union building.
The Odessa bloodshed came on the same day that Kyiv launched its biggest push yet to reassert control over separatist areas in the east, hundreds of miles away.
On Saturday, Kyiv pressed on with the second day of that offensive. Ukrainian soldiers and pro-Russian rebels fought fierce battles around the eastern flashpoint of Slavyansk, with only a small reprieve to allow a team of European military observers to pass through.
The seven-person team, which was freed on Saturday, had been held hostage for eight days.
On the outskirts of Slavyansk, AFP journalists witnessed a ferocious firefight on Saturday between Kalashnikov-armed insurgents and pro-Kyiv soldiers. At least nine people have died in clashes around Slavyansk.
The rebels there aim to hold a referendum on May 11 on secession from Ukraine, similar to one staged in Crimea in March.
The violence in Odessa showed how the conflict has spread from the eastern separatist heartland to an area far from the Russian frontier, tipping the country of 45 million closer to war.
Odessa is located in the southwest of Ukraine, far from the eastern areas held by the rebels and far from the Russian frontier where Moscow has amassed troops. But it is close to Moldova's Transdniestria region, where Russia also has troops.
The Kremlin, which has massed tens of thousands of soldiers on Ukraine's eastern border and proclaims the right to invade to protect Russian speakers, blamed the deaths on Kyiv and its Western backers.
Kyiv said the violence was provoked by foreign demonstrators sent in from Transdniestria. It said most of the dead who had been identified so far were from there.
On Saturday morning, people placed flowers near the burnt-out doors of the trade union building in Odessa, lighting candles and putting up the yellow, white and red flag of the city.
The burnt remains of a tented camp of pro-Russian demonstrators nearby had been swept away. People spoke of their horror at what happened.
About 2,000 pro-Russian protesters gathered outside the burnt-out building, chanting: "Odessa is a Russian city."
At the nearby hospital, residents queued up to offer blood and others tried to find out what medicine was needed so they could go out to buy it.
Oleg Konstantinov, a journalist covering the events for a local website, said bullets had flown in the melee before the blaze: "I was hit in the arm, then I started crawling, and then got hit in the back and leg."
On Saturday, Kyiv said it was pressing on with its offensive in the east for a second day, and had recaptured a television tower and a security services building from rebels in Kramatorsk, a town near Slavyansk.
"We are not stopping," Interior Minister Arsen Avakov said in a Facebook post. "The active phase of the operation continued at dawn."
Rebels in Slavyansk shot down two Ukrainian helicopters Friday, killing two crew, and stalled an advance by Ukrainian troops in armored vehicles.
Vasyl Krutov, head of a government "anti-terrorist center" behind the operation in the east, told a news conference there was gunfire and fighting around Kramatorsk: "What we are facing in the Donetsk region and in the eastern regions is not just some kind of short-lived uprising, it is in fact a war."
Kremlin spokesman Dmitry Peskov said Kyiv and the West are to blame.
"Kyiv and its Western sponsors are practically provoking the bloodshed and bear direct responsibility for it," Peskov was quoted as saying by RIA Novosti.
He said Friday's violence made the idea of Ukraine holding presidential elections on May 25 "absurd."
Ukraine's acting President Oleksander Turchinov said he and his people are being "pushed into confrontation."
"Today we Ukrainians are constantly being pushed into confrontation, into civil conflict, toward the destruction of our country to its heart," he said. "We cannot allow this to happen and we must be united in the fight against a foreign enemy."
The release of the military monitors from the Organization for Security and Cooperation in Europe resolves a major diplomatic issue for the West. The separatists had captured the team on April 25 and described them as prisoners of war.
One Swede was freed earlier on health grounds while four Germans, a Czech, a Dane and a Pole were still being held until Saturday. A Russian envoy helped negotiate their release.
The separatist leader in Slavyansk, self-proclaimed "people's mayor" Vyacheslav Ponomaryov, said they were freed along with five Ukrainian captives, with no conditions.
"As I promised them, we celebrated my birthday yesterday and they left. As I said, they were my guests."
The OSCE team's leader, German Col. Axel Schneider, speaking on the road out of Slavyansk after being freed said: "You can imagine, it's a big relief. The situation was really tough. The last two nights when you see what was going on, every minute gets longer."
He praised his captor Ponomaryov as "a man whose word counts a lot. He's a man who listens."
The West has made clear it will not use military force to protect Ukraine but will rely on economic sanctions against Moscow to, in the words of US President Barack Obama, change Putin's "calculus."
So far Moscow has shrugged off sanctions, which so far have included measures only against individuals and small companies.
Obama and Merkel said Friday they would seek tougher measures, including hitting whole sectors of the Russian economy, if Moscow interferes with Ukraine's May 25 vote.
Agence France-Presse and Thomson Reuters contributed to this report.