Visa to Belarus when traveling Belarus-Russia-Belarus

Let's separate chaff from grain in your considerations at first. You have 3 legs in your trips:

1. Europe - Belarus. You are arriving by air to MSQ, yeah?

5-day visa-free regime perfectly applies to this leg, no matter where you are heading further (to Russia, to Jamaica or somewhere else), except when you do direct transit to Russia, see next point.

2. SPB - Belarus (2h) - Europe. I assume you are flying from LED to MSQ again, so you are eligible for visa-free transit as your hop is only 2 hours, whilst the allowed transit duration is 24h.

Transit passage (transit) of foreign citizens through the territory of the Republic of Belarus without transit visas is possible:
...

• when flying to the country of destination using international airlines with a stop-over at the airport of the Republic of Belarus, provided that the passengers have documents granting entry to the country of destination and air tickets with the confirmation of the date of departure from the transfer airport, if the period of stay in the territory of Belarus does not exceed 24 hours. In this case, the passengers are not allowed to leave the designated area of the airport;
  ...

UPDATE: after verification of a bunch of disjointed and controversial information regarding transit to Russia, the final conclusion is NO. Transit foreigners arriving in Minsk and departing to Russia are not covered by this visa-free regime, because BY-RU flights are loaded from domestic zones of MSQ airport and don't undergo border control.

This is also explained in this official comment in Deutsch or Russian (sorry, didn't find English version). Pay attention to fifth question in the above FAQ.

And, as ground BY-RU transit is totally prohibited to foreigners, your only escape is a full-featured entry/transit Belarusian visa.

The bottom line: going to Russia after being 5 days in Belarus is not equal to direct transit to Russia via Belarusian airport. The former is allowed without Belarusian visa, whilst the latter is does not.

UPDATE: according to recent report, Russia and Belarus signed an agreement about mutual recognition of visas, so having a visa of any gives you right to enter/pass both countries

I did a research on the matter from here in Minsk.

1. Foreigners must cross through international checkpoints in either direction: there is only one land crossing (and nothing there) at the BY-RU border and it's unpractical which limits all other options to flights.

2. There is passport control in Russia, but not necessarily an efficient one - a US traveler recently handed in the second part of his migration card in Russia though he was leaving for Belarus (don't do that - keep it). There is no inbound border control for flights from Russia here in Minsk.

3. BY-RU flights are no longer domestic.

I hope that makes sense)

A