An Associated Press reporter counted 225 of the white tarp-covered trucks as they drove from Ukraine into a Russian border town called Donetsk, which bears the same name as the largest rebel-held city in Ukraine. A second AP reporter on the Ukrainian side of the border was able to look inside about 40 of the tractor-trailers side and confirmed they were empty.
One driver who declined to give his name said the rest of the 260-truck convoy was expected to return within hours to Russia. The state news agency RIA Novosti cited the Russian customs service as saying the trucks were moving in six groups.
The trucks had crossed Friday into Ukraine bound for Luhansk, another rebel-held city in eastern Ukraine hard-hit by weeks of fighting between Ukrainian forces and pro-Russian rebels. The Ukrainian government and Western countries denounced the move as a violation of Ukraine's sovereignty and accused Russia of using the convoy to smuggle supplies and reinforcements to separatist fighters.
Russia said the trucks carried only food, water, generators and sleeping bags. When some of the trucks were inspected by reporters a few days previously, some of those items were visible in the cargo.
In a separate development, NATO said it has mounting evidence that Russian troops are operating inside Ukraine and launching artillery attacks from Ukrainian soil. Russia also rejected that accusation.
German Chancellor Angela Merkel, who has advocated a measured European Union response to Russia's aggressive policies in Ukraine, arrived Saturday in Kiev to meet Ukrainian President Petro Poroshenko.
In a statement, Merkel said she would advise Poroshenko "that the conflict can only be resolved politically and that a cease-fire must be reached as soon as possible."
It remained unclear Saturday what the Russian convoy had actually delivered, or how. Unloading hundreds of trucks in less than a day in a war-battered region represents a sizeable task. AP journalists who followed the convoy to Luhansk on Friday said rattling sounds from some trailers indicated they were not fully loaded.
The convoy's entry caused Russia-Ukraine tensions to spike. The trucks had languished on the Russian side of the border for nearly two weeks as Ukraine refused permission for entry and the Red Cross sought security guarantees from all sides.
Russia sent the trucks in Friday, saying it had lost patience and Luhansk was on the edge of a humanitarian catastrophe. Ukraine condemned it as a "direct invasion."
At the United Nations in New York, Russian Ambassador Vitaly Churkin rejected NATO's accusations that Russian troops 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.
Ukraine has retaken control of much of its eastern territory bordering Russia, but fighting for Donetsk and Luhansk persists.
Unrest in eastern Ukraine began in mid-April, one month after Russia annexed Ukraine's Crimean peninsula. 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 Izvarnye, Ukraine, contributed to this report.
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