Learn Russian: Министр якобы опровергал эту дезинформацию. - The minister allegedly refuted this misinformation.

The particle якобы means allegedly or supposedly. By using it here, the speaker expresses doubt that the minister actually refuted the misinformation. It signals that this is a claim being made, but the speaker does not necessarily believe it is true.

Could we use мол instead of якобы in this sentence?

Yes, but it changes the focus. The particle якобы highlights the speaker's doubt about the event. The particle мол is used to relay hearsay, acting like a spoken quotation mark. If you used мол, it would mean the minister himself went around saying he refuted it, and you are just passing his words along.

Why use the imperfective verb опровергал instead of the perfective опроверг?

Using the imperfective опровергал focuses on the general fact that the action took place, or means he was trying to refute it over a period of time. The perfective опроверг would mean he successfully and definitively refuted it once and for all. Paired with якобы, the imperfective makes the minister's denial sound even less convincing.

Does якобы have to go right before the verb?

It usually goes immediately before the specific word the speaker is casting doubt on. Here, it is placed before опровергал because the doubt is about the action of refuting. If you wanted to say the minister definitely refuted something, but you doubt it was this specific topic, you would move the particle and say Министр опровергал якобы эту дезинформацию.