Think of the thriller “Silverton Siege” as a South African “Dog Day Afternoon” — a hostage situation, a bank surrounded and a tense stand-off with potent political implications.

Director Mandla Dube and a superb cast deliver a tight and tense true story that hews to genre formula because that’s what hostage thrillers all do. There are just a couple of ways this all ends, after all.

But stars Thabo Ramatesi, Noxolo Dlamini and Stefan Erasmus animate a wildly-improvised 1980 day of political terrorism, designed to “make this country ungovernable,” tumbling into Plan C after Plan A is aborted and Plan B — their escape — is foiled. And with his first produced screenplay, Sabelo Mgidi makes a wry, raw comment on the delusions of “racial purity” at a moment when Apartheid finally started to crack.

Four “freedom fighters” were set to blow up the tanks at a huge fuel storage facility. But cagey, experienced Calvin Khumalo (Rametesi) smells a trap just before it springs. They escape in their van, only to be chased all over Pretoria, losing one of their number in the process.

Captain Langerman (veteran South African heavy Arnold Vosloo) has them cornered, at last. That’s when they storm into a bank, take its diverse population of racially segregated customers hostage, and try to bargain their way out.

Things get really interesting when their negotiated escape goes wrong, and Khumalo decides that whatever transpires, this just became bigger than these three and their hostages.

“What’s the price of freedom? EVERYTHING.”

The “true story” angle immunizes the picture — somewhat — from any tendency to mutter “Oh come on!” Some of the sermonizing you have to figure was invented, the “non violence” ethos declared by the freedom fighters sanitizes them and as character names were changed, other elements aren’t the literal truth.

There’s an African American boxing promoter (Shane Wellington) in line, irked at overt racism by some Boer on the staff — “I ‘m from Tuscaloosa, Alabama. I deal with dumbass rednecks all the time!” — and even more irked when the freedom fighters threaten his safety, his livelihood and his bedazzled briefcase full of cash.

“We have an American citizen in here,” slows the roll of the police, with an officious martinet who has his own SWAT team showing up.

A priest, a South Asian man, a woman of mixed-race “passing” and a bank supervisor (Elani Dekker) with her own complicated racial history are among the other hostages. And some bull-necked bigot bank security chief figures he gets to decide who is “white?”

That adds weight to a movie that does well enough with the standard hostage drama situations — bickering amongst the hostage takers, “Stockholm Syndrome” with a hint of racial tolerance to it among the hostages, escalating stakes as demands are met or delayed.

Ramatesi, Dlamini as the female firebrand Terra and “pregnant wife” gunman Aldo (Erasmus) are terrific leads, giving us layered characters with competing agendas in a generally brisk and taut tale.

“Silverton” may be more on-the-nose with its messaging than in its literal history. But making his second feature film, Dube gets a heroic yarn out of a fairly conventional genre piece and sets a couple of fresh faces up for stardom in the process. After all, “Dog Day Afternoon” was fictionalized, too.

Rating: TV-MA, violence, profanity

Cast: Thabo Ramatesi, Noxolo Dlamini, Arnold Vossloo, Stefan Erasmus, Elani Dekker and Shane Wellington

Credits: Directed by Mandla Dube, scripted by Sabelo Mgidi. A Netflix release.

Running time: 1:41