Russia is sending 280 trucks barreling toward eastern Ukraine as part of what it says is an aid convoy to help Ukrainian civilians effected by the worsening fighting there. But Ukrainian officials say they will not allow the trucks to cross into Ukraine because they believe they are a clandestine invasion force. It's not hard to see why: a few months earlier, Russia sent undercover special forces into the Ukrainian region of Crimea as the vanguard of a hostile invasion, which quickly annexed the territory.

Russia, never great at public relations abroad, is giving Ukraine reasons to worry, and not just because it is actively arming and supplying the eastern Ukrainian separatists who are causing the violence there. On Wednesday, for example, the aid convoy made a mysterious and unannounced stop at a Russian military base — no one is sure why. Russia will not reveal the contents of the trucks.

Now, the Guardian's correspondent Shaun Walker spotted what appear to be two Russian military helicopters, armed to the teeth, flying alongside the supposedly civilian convoy:

Two helicopters accompanying the convoy, flying extremely low. Now sat in the fields alongside pic.twitter.com/yYTr7Vhp8C — Shaun Walker (@shaunwalker7) August 14, 2014

Russian military aficionados on Twitter identified the aircraft as a Mil Mi-17 military helicopter; NATO calls it a Hip and Russia identifies is as the MI-8M. While it is true that the Mi-17 is a multi-purpose aircraft often used for transportation, it is very difficult to miss that this one is armed with a whole bunch of missiles.

You have to wonder, then, who Russia expects to fire those missiles on. The fighting in eastern Ukraine is between separatist rebels who are backed by the Russian government (and staffed by a number of Russians) versus the Ukrainian military. Russia presumably is not planning on engaging in combat with the rebels it also backs, hence the concerns that Russia wants all this military force to battle the Ukrainians.

As Russian official rhetoric has maintained that Moscow is uninvolved in the conflict and wants to see it end peacefully, the Russian military has become more and more overtly involved on behalf of the rebels. The US recently released satellite photos showing Russian artillery in Russia firing openly at Ukrainian military positions, confirming a long-standing Ukrainian insistence that Russia was committing overt acts of war. The eastern Ukrainian city of Donetsk, a center of the fighting, has been struck by a number of artillery shells (it is not clear who fired them) that are killing civilians there.

Russian President Vladimir Putin said recently of the convoy, in a line that could be read as somewhat ominous, "We will do everything we can to help secure an end to this conflict as soon as possible, so that there will be no more bloodshed in Ukraine."

Maybe Putin is sincere that this aid convoy is just an aid convoy. But given that Russia invaded and annexed Crimea just a few months ago with a similarly covert invasion — something Putin proudly admitted after he finished annexing Crimea — it it not hard to understand fears that this could be another Trojan Horse, and one flanked by heavily armed Russian military helicopters.