KIEV - Intense fighting in Ukraine, including a rocket strike on Kiev's military headquarters in the east, killed at least 20 people on Tuesday on the eve of a four-way peace summit.
Pro-Russia rebels sought to encircle railway hub Debaltseve, and Ukrainian forces launched a counter-offensive around the strategic port of Mariupol as diplomats scrambled to finalise a deal to end the 10-month war at the summit in Minsk planned for Wednesday.
Ukrainian President Petro Poroshenko said rockets from a Tornado multiple launch system for the first time hit the military's command centre in Kramatorsk, a regional capital behind the frontlines considered to be under firm government control and far from rebel positions.
Local officials said the strike killed at least six people and wounded 21 in nearby residential areas.
Foreign ministry official Dmytro Kuleba tweeted that the rockets were Tornado, "Russia's newest Multiple Launch Rocket System. Ukraine simply doesn't have it." Kiev and the West accuse Moscow of supplying and training the heavily armed separatists, but Russia denies the claims.
Rebels say their weapons have been captured from Ukrainian forces, although Kiev has cited numerous cases of the insurgents using advanced weapons that are only available from Russian arsenals.
Another seven Ukrainian soldiers and seven civilians were killed in fighting over the last 24 hours, Kiev officials and rebels said, including in Debaltseve which the insurgents claim to have surrounded.
Despite growing diplomatic momentum, Ukrainian forces took control of three villages east of Mariupol, around 90 kilometres (60 miles) south of the rebel stronghold Donetsk, and fierce fighting was going on for control of two more, senior interior ministry advisor Zoryan Shkiryak said.
Rebels, diplomats and mediators gathered in the Belarussian capital to bridge gaps on a possible peace deal, which the leaders of Ukraine, Russia, France and Germany hope to sign in Minsk on Wednesday.
Rebel negotiator Denis Pushilin told the separatists' news agency that he was heading to Minsk for talks with mediators from the Organisation for Security and Cooperation in Europe (OSCE) as well as Russian and Ukrainian representatives.
French President Francois Hollande and German Chancellor Angela Merkel have been conducting frantic diplomacy, taking the "last chance" deal to Poroshenko and Russian leader Vladimir Putin.
Merkel was in Washington Monday for lengthy talks with the US President Barack Obama on the initiative to defuse fighting that has killed at least 5,400 people since April.
No arms, yet
Obama agreed to hold off on sending arms to Ukraine until truce efforts have played out.
Proponents of sending arms to Ukrainian forces argue that Kiev needs the weapons to counter advanced Russian hardware.
But Merkel has opposed sending arms, amid fears that the Ukraine conflict could become a proxy war between Russia and the West.
But some in the West feel hi-tech weapons could at least make the conflict more costly and painful for Russia, already reeling under the impact of US and EU sanctions.
Merkel acknowledged in Washington that a drive to get Putin to put his name to a deal may not succeed.
"I cannot give you a guarantee for the outcome of the Wednesday talks and maybe nothing will come out of it." Ahead of the Minsk summit, the European Union decided to hold off implementing new sanctions against Russia.
Putin has warned that a "number of points" still needed to be agreed before the Minsk meeting can take place.
Based on a largely ignored peace deal agreed in September in Minsk, the new plan may extend rebel control over territory seized in recent weeks, around 500 square kilometres (around 200 square miles), although Kiev is adamant the demarcation line agreed in September should not be shifted.
Hollande has said the proposal includes the creation of a 50 to 70-kilometre (31 to 44-mile) demilitarised zone around the current frontline.
'Very complicated' talks
"Eight days ago, they (Ukraine and Russia) weren't talking to each other. Now, they've sat at the same table," a French diplomatic source said, describing negotiations as "very complicated".
Contentious issues include the degree of future autonomy in the east and Kiev's insistence on retaking control of the roughly 400-kilometre border between separatist Ukraine and Russia.
The deployment of peacekeepers is also being discussed, but there is so far no agreement on their nationality.
"If we accept armed Russians as part of the force, you're de facto legitimising the presence of their troops on our soil," a Ukrainian diplomatic source said.