MINSK: Russian President Vladimir Putin urged his Ukrainian counterpart Tuesday not to escalate an offensive against pro-Moscow rebels, and threatened economic retaliation for signing a trade accord with the European Union.
At the leaders' first meeting since June, Ukrainian President Petro Poroshenko replied by demanding a halt to arms shipments from Russia to the separatist fighters.
The pair shook hands at the start of talks in the Belorussian capital Minsk, only hours after Kiev said it had captured Russian soldiers on a "special mission" on Ukrainian territory.
Responding to a video of the detained servicemen, a Russian Defense Ministry source told Russian news agencies that the servicemen had crossed the border by mistake.
Moscow has long denied charges by Kiev that it has been sending weapons and fighters to help the separatists in eastern Ukraine. The United States and European Union have backed Kiev by imposing sanctions on Moscow in a standoff that has prompted both Russia and NATO to step up military maneuvers.
"We are convinced that today, (the Ukraine crisis) cannot be solved by further escalation of the military scenario without taking into account vital interests of the southeastern regions of the country and without a peaceful dialogue with its representatives," Putin said.
He said the Russian economy could lose about $2.8 billion if European goods reached its markets via Ukraine after Kiev signed the trade deal with the EU in June. Moscow would retaliate with trade measures if that were to happen, Putin added.
Poroshenko responded by defending a peace plan he issued in June, when the rebels in the southeast Donbass region scorned his invitation to lay down their arms and leave by a safe corridor.
"The prime condition for a stabilization of the situation in Donbass is the establishment of effective control over the Russian-Ukrainian border. It is vital to do everything to stop deliveries of equipment and arms to the fighters," he said.
More than 2,000 people have been killed since April in the fighting, but the Ukrainian army has now largely pinned the rebels down in two eastern strongholds.
EU foreign policy chief Catherine Ashton and the leaders of Belarus and Kazakhstan were also taking part in the Minsk meeting, the first between Putin and Poroshenko since June 6.
Poroshenko pointedly mentioned the other participants by name, but not Putin, referring only to "the presence of the leadership of the Russian Federation."
Russia has called for a cease-fire many times and supports what it calls "a dialogue of national unity" which would boost the authority of Ukraine's regions.
But a unilateral cease-fire by Kiev in June was widely seen by Ukrainians as allowing the rebels a breathing space to regroup, and Poroshenko could find it difficult to win support at home for a repeat, especially as government forces have the upper hand.
Ukraine will also resist any settlement that could give the eastern regions more power over policy decisions, potentially blocking moves by Kiev to shift closer to the EU or NATO.
"Most likely, it's difficult to expect any colossal breakthrough today but we should start progress towards peace," said Belorussian President Alexander Lukashenko, who is hosting the meeting.
The risk of outright war between Russia and Ukraine, the two most populous former Soviet republics, has alarmed Washington and its NATO allies, while tit-for-tat sanctions between Moscow and the West are threatening to tip the Russian economy into recession and choke off recovery in Europe.
Earlier Tuesday, a day after announcing it had detained 10 Russian paratroopers who crossed the border in a column of armed infantry vehicles, Ukraine released video of the captive soldiers.
In footage posted on the official Facebook page of the Ukrainian government's "anti-terrorist operation," the men were shown dressed in camouflage fatigues. One of them, who identified himself as Ivan Milchakov, listed his personal details, including the name of his paratroop regiment, which he said was based in the Russian town of Kostroma.
"I did not see where we crossed the border. They just told us we were going on a 70 km march over three days," he said.
Another man in the footage, who gave his name as Sergeant Aleksei Generalov, said: "Stop sending in our boys. Why? This is not our war."
Russian news agencies quoted a Defense Ministry source as confirming that Russian servicemen had crossed into Ukraine but saying they did so inadvertently.
"The soldiers really did participate in a patrol of a section of the Russian-Ukrainian border, crossed it by accident on an unmarked section, and as far as we understand showed no resistance to the armed forces of Ukraine when they were detained," the source said.
Ukraine rejected that explanation. "This wasn't a mistake, but a special mission they were carrying out," military spokesman Andriy Lysenko said in a televised briefing.
He also said separatists were attacking the southeastern border town of Novoazovsk "at this very minute" and Ukrainian forces had destroyed 12 armored infantry vehicles in the area.
Twelve Ukrainian service personnel had been killed in fighting in the past 24 hours, he said, including four border guards who died when Russian Mi-24 helicopters attacked a frontier post in Luhansk region Monday.