The Ukrainian president has told Sky News he has evidence that Russian military tanks are massing along his country's border.
Petro Poroshenko has shown Sky News images of what he claims are tanks lining up along the border, close to where Russia stores its ammunition.
Russia has seized three Ukrainian navy ships and their crew in the Kerch Strait after accusing them of venturing into their territorial waters.
The president enacted martial law for some provinces for a limited period after parliamentary support.
He told Sky’s Alex Rossi: "This is the tank base just 18km from our border, this was happening in September, October, and now.
“This is 18km from my border, this is the same warehouse where they have their ammunition, the same where they have multi-rocket launch systems, we should be prepared to protect my country.
"If the whole world has no reason to trust Putin, Ukraine definitely doesn't have a reason to go with him."
It comes as countries look to speak to the Russian president at the G20 in Argentina about the seizure of ships and a separate meeting between Putin and Donald Trump being cancelled.
Moscow denies restricting any shipping to Ukraine and President Putin described the Ukrainian reaction to the incident as ‘a pretext to introduce martial law’.
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