After I failed to purchase AA early access from mailru website with my UK Visa, I found a slightly different way of paying for the game using terrabank.ru services, since it offers two different payment methods (to be honest, no idea what is the difference between them two) to use Visa/MasterCard and only one of them finally worked for me.
Here is a small guide for where to find links and how to navigate through payment process. Hope it helps!
After entering your card details on main mailru website you get this message:
"Не удалось произвести оплату. Пожалуйста, убедитесь в правильности ввода параметров и повторите попытку"
"Unable to make the payment. Please make sure your details are correct and try again"
Scroll down and press the link at the bottom.
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You will be taken to terrabank.ru where you can choose a different payment option. This link should take you directly to step 2, since you were logged in on main mailru website you don't have to update your details.
Just use the drop-down box to select payment option you want and press Select (Visa/MasterCard2 option worked for my UK Visa).
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Next, enter the amount of crystals you want to purchase and confirm the payment.
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After confirming you should get a notification about payment being successful, refresh your account on main mailru website - crystals should be there.