The Russians may flaunt theirs, but other nations are more coy about their thermobaric and fuel-air weapons. Such weapons have a reputation as being brutal and barbaric, and are sometimes hyped as "the poor man's nuke." Certainly any extremely powerful explosive device is indiscriminate, if not an actual weapon of mass destruction. So it's not surprising that there accusations fly about other nations developing or using them.
So we get stories like this one in UPI: "Document describes Iran 'fuel-gas bomb'":
It's not impossible that Iran is developing fuel-air weapons. But any country with a lot of oil is also likely to suffer from accidental explosions, like the one in 2004 which killed over 200 people when vapor from several fuel wagons produced a blast so violent that "Iranian seismologists recorded a quake of magnitude 3.6 at the time of the explosion." So it's quite possible that the research is simply what it appears to be.
Similarly, Israel was accused of using fuel-air weapons against civilians in Lebanon in 2006 (sometimes even described as chemical weapons) -- but it seems more than likely that they were simply used for mine clearance.
The value of such accusations seems to be more about painting the other side as being barbaric and inhumane -- regardless of what weapons are used or their actual effects. Rational debate is scarce in this field, and the argument is likely to be won by the headline that screams loudest.