loud explosions "in as many minutes around noon" - I don't understand

Source: Fighting rages in rebel-held city in eastern Ukraine; govt demands that rebels surrender

Conditions were clearly deteriorating in Donetsk, the largest rebel stronghold in eastern Ukraine. Associated Press reporters heard 25 loud explosions in as many minutes around noon. According to city council spokesman Maxim Rovinsky, at least one person was killed and 10 injured in shelling overnight, as more than 10 residential buildings, a hospital and a shop were heavily damaged in the fighting.

Alright, they heard 25 load explosions around noon. Fine. Makes perfect sense. But how does in as many minutes fit into the sentence grammatically? And what does that even mean?

25 loud explosions in as many minutes

It means 25 loud explosions were heard in 25 minutes, around noon. The in as many minutes phrase is used to depict the exact numerical amount of time(in minutes) through which explosions were heard.

Take a look at the title of this article:

NASA launching five rockets in as many minutes in ATREX weather study

From the first paragraph of the article:

The $4 million ATREX — Anomalous Transport Rocket Experiment — program will launch five different rockets within a span of five minutes from the Wallops Flight Facility in Virginia; the rockets will then release chemical tracers between 50 to 90 miles up into the sky.

As you can see from the quoted sentences, "launching five rockets in as many minutes" is a concise way of saying Nasa will launch five different rockets within five minutes.

Therefore, the phrase "in as many minutes" is especially used in sentence construction when you have the same number repeating in another part of the sentence, describing a different construct(ex: time/number). Although the other way of writing the sentence(the number expanded both times) wouldn't be deemed incorrect, this way is preferred for its brevity.