DONETSK, Russia — Hundreds of trucks from a bitterly disputed Russian aid convoy to rebel-held eastern Ukraine rolled back across the border Saturday into Russia but questions about alleged Russian artillery in Ukraine still remained.
NATO said Friday it has mounting evidence that Russian troops are operating inside Ukraine and launching artillery attacks at Ukrainian troops from Ukrainian soil as well as from Russia. Moscow's ambassador to the U.N. vehemently rejected that accusation.
Paul Picard, head of the border observation mission for the Organization for Security and Cooperation in Europe, told journalists in the Russian town of Donetsk that all the vehicles that had crossed into Ukraine had returned to Russia by mid-afternoon. Deputy Emergencies Minister Eduard Chizhkov was quoted as saying 227 vehicles had taken part.
An AP reporter on the Ukrainian side of the border was able to look inside about 40 of the white-tarpaulined tractor-trailers and confirmed they were empty. Russia said the trucks carried only food, water, generators and sleeping bags to the hard-hit rebel stronghold of Luhansk.
Russia had unilaterally sent the trucks into Ukraine through a rebel-held border point Friday, saying it had lost patience with Ukraine's delaying tactics. Ukraine promptly called the act an invasion.
Ukraine and others — including the U.S., the European Union and NATO — denounced the Russian move as a violation of Ukraine's sovereignty. Kiev and Western countries also suggested the convoy could be used to smuggle supplies and reinforcements to pro-Russian separatists fighting the government.
German Chancellor Angela Merkel, who has advocated a measured EU response to Russia's aggressive policies in Ukraine, met Saturday in Kiev with Ukrainian President Petro Poroshenko and urged a political solution to the crisis.
Poroshenko will be meeting Russian President Vladimir Putin in Minsk on Tuesday in their first encounter since June. Merkel said she was looking forward to the outcome of those talks and expressed "hope that at least a step forward will be reached there."
Poroshenko said Ukraine is anxious to bring peace as soon as possible and solve the conflict by talks, but "not at the expense of sovereignty, territorial integrity and independence of Ukraine." The rebels in the east have declared the region independent and some have sought to be annexed by Russia.
Ukraine has retaken control of much of its eastern territory bordering Russia in the last few weeks, but fierce fighting for the rebel-held cities of Donetsk and Luhansk persists.
Asked what message he intended to convey to Putin next week, Poroshenko said "take away your armed people from our territory and I can promise peace will come to Ukraine very soon."
It remained unclear Saturday what the Russian convoy had actually delivered, since it only arrived late Friday afternoon. Unloading hundreds of trucks in just a few hours in a war-battered region represents a sizeable task. AP journalists following the convoy to Luhansk said rattling sounds Friday from some of the trucks indicated they were not fully loaded.
At the United Nations in New York, Russian Ambassador Vitaly Churkin rejected NATO's accusations that Russian troops and artillery were inside Ukraine. Russia has steadfastly denied supporting and arming the rebels.
In the Ukrainian city of Donetsk, residents reported artillery strikes throughout Friday night and Saturday morning. The mayor's office said three people were killed, including two who had been waiting for a bus.
Unrest in eastern Ukraine began in mid-April, one month after Russia annexed Ukraine's Black Sea peninsula of Crimea. The United Nations says more than 2,000 people have been killed and 340,000 forced to flee their homes during the fighting.
Associated Press reporter Mstyslav Chernov in Izvaryne, Ukraine, Nataliya Vasilyeva in Kiev and Jim Heintz in Moscow contributed to this report.