[Jaded]

Twenty militants were killed in more than 10 hours of gunfights with security forces, 10 of them Arabs.

Seems to me the sentence should read:

In more than 10 hours of gunfights with security forces, twenty militants were killed, 10 of them Arabs.

[SAJ]

Precisely so. As phrased, the Russian security forces included 10 Arab troops -- a statement almost certainly false on its face, and no one cares about the ethnic makeup of the security forces in any case. OTOH, 10 dead Arabs is a newsworthy fact here, considering the location of the events.

The most economical way to express the desired sentiment is probably something like:

Twenty militants, 10 of them Arabs, were killed in more than 10 hours of gunfights with security forces.

Heavy odds the ''journalist'' is a refugee from the pulbic skoolz using a 10th Ed. University of Chicago stylebook (if, indeed, any stylebook at all).