Who's selling and who's buying?

Just found this disturbing report regarding some worrisomely big weapon bazaar in Qurna, the largest town at the center of the triangle formed by Basra, Nasiriya and Amara.
Qurna is located 6 kilometers from the Iranian border, population around 100,000 with a strong presence for Sadrists and there's a story running among thr locals that their town was the spot where Adam first landed at on earth after he was expelled from heaven.

Anyway...

I've been to Qurna many times during my internship in the northern suburbs of Bsara and I heard a lot from the locals about the huge weapon business in the area but it seems that with time, the quality of the business had grown wild; at that time, they mostly sold pistols, ak-47s and grenades. By the way the latter are a famous fishing tool in Iraq!
But now there are a few more exotic items on the menu:

Residents said the trade was not confined to small arms. They said smugglers openly put for sale mortars, rockets and landmines.

Those weapons are certainly remnants of the Iraq-Iran war. Says who? Says the dealers themselves!

The source of the weapons is not known. The smugglers say the weapons are remnants of the 1980-1988 Iraq-Iran war.

But some former military personnel think that's not the case:

Recently, new weapons were being brought to the area. Residents, who served in the former army, said they had not seen such weapons before.
“Some of these (smuggled) weapons were not used by the former army. They are new to us and look modern. Some of the items on show fall under the heavy weapons category,” a resident said.

So the question is, if those were weapons sent by Iran to the militias to help them carry out attacks on coalition forces like many of us already think, why would the militias sell the weapons?

The only explanation I can find is that Iran is sending enough weapons and munitions to the extent that the militias can feel well armed and at the same time make some good bucks.
But again, this theory brings up another question, that is who is buying the excess weaponry?
I can think of the tribes as a likely potential customer for grenades and even for mortars since I know from spending a whole year over there that there had been times when tribes used mortars against each other during some nasty conflicts but who is buying the landmines? Any suggestions?