Ukraine crisis: Russian lorries leave as Merkel visits
All the lorries from an unauthorised Russian aid convoy have now crossed back over the border from Ukraine.
The convoy returned from the eastern city of Luhansk, which is held by pro-Russian separatists. Kiev and Western officials fear the trucks may have had military equipment to help the rebels.
Russia said they had delivered generators, food and drink.
Meanwhile, Ukraine is to receive a 500m-euro (£400m) loan from Germany, Chancellor Angela Merkel said in Kiev.
The money will be used to help rebuild the country's damaged infrastructure, Mrs Merkel said in a joint press conference with President Petro Poroschenko in the Ukrainian capital on Saturday.
A further 25m euros will go toward helping refugees, she said.
Four months of fighting in eastern Ukraine have left more than 2,000 people dead. More than 330,000 people have fled their homes.
The violence erupted when pro-Russian separatists in the Donetsk and Luhansk regions declared independence from Kiev, after Russia annexed the Crimean peninsula from Ukraine in March.
Ukraine accuses Russia of arming the rebels and sending Russian soldiers into eastern Ukraine - a claim denied by the Kremlin.
Analysis: David Stern, BBC News, Kiev
The circumstances of Angela Merkel's visit to Ukraine have shifted dramatically in the last 24 hours. When it was first announced, days ago, it seemed to be building on the momentum of Ukrainian troops' apparently successful campaign against insurgent forces in the country's east.
Now, however, Moscow's unilateral decision on Friday to send in an aid convoy without Kiev's permission has raised the tensions, and the stakes, even further.
But the symbolic importance of Ms Merkel travelling to Kiev has not changed. She is said to be the European leader with whom Russian President Vladimir Putin shares the closest working relationship.
Her standing next to Ukrainian President Petro Poroshenko sends a clear message to Mr Putin, a week before the two men are due to meet in the Belarusian capital Minsk. However, whether this will make a difference is another question.
Prior to her arrival in Kiev, Mrs Merkel described the Russian convoy's movement into Ukrainian territory as a "dangerous escalation".
Observers from the Organization for Security and Co-operation in Europe (OSCE) said there was no information about what most of the convoy - of more than 200 vehicles - was carrying.
The head of the OSCE mission, Paul Picard, told the BBC that only the first 37 trucks had been inspected by the Red Cross before they set off into Russia.
The lorries had already been waiting at the border for a week, while Russia, the Ukrainian government and the Red Cross tried to come to an agreement on their passage.
The Russians said the convoy started moving because it could not wait any longer, owing to the worsening humanitarian situation in eastern Ukraine, which is held by pro-Russian separatists.
The White House and the Ukrainian government both described the deployment of the convoy as a flagrant violation of Ukraine's sovereignty.
In a phone call, US President Barack Obama and Mrs Merkel said the conflict had "continued to deteriorate" since a Malaysian airliner was downed last month over rebel-held territory, with the loss of all 298 people on board.
Ukraine called the Russian convoy a "direct invasion" of Ukraine.
Nato and the European Union have also criticised what they said was a violation of Ukraine's sovereignty.
Nato officials have accused Russia of building up troops on its border, saying significant numbers of Russian forces are operating within Ukraine, using artillery.
But speaking to the UN Security Council, Russia's UN ambassador Vitaly Churkin accused Western powers of distorting reality.
"Sometimes it reminded me of the kingdom of crooked mirrors because some members of the Council were not concerned about the fact hundreds of civilians are dying."
He said Russia had to act to save perishable goods and that he hoped the Red Cross would help distribute the aid.
"We waited long enough. And it was time to move, and this is what we did," he said.