Al-Qaeda in the Arabian Peninsula has stepped up its campaign to stamp out use of the mild narcotic qat in a Yemeni city it controls, announcing hefty fines for traffickers.

Chewing wads of the evergreen herb has a stimulant effect similar to drinking numerous cups of strong coffee, and it is part of the social fabric of Yemen.

But a month after AQAP seized control of Hadramawt provincial capital Mukalla in April, it banned the sale and consumption of qat there.

The prohibition has apparently not worked.

Residents said members of the extremist group plastered posters on walls across the city late Wednesday setting fines on the trade in qat.

Every trafficker arrested with a quantity of up to 10 kilogrammes (22 pounds) of qat will be fined 500,000 riyals ($2,500/2,252 euros), the posters warn.

If the amount is between 10 and 100 kilogrammes, the dealer faces a fine of one million riyals.
And if the amount exceeds that, his vehicle will be seized.

AQAP has exploited months of fighting in Yemen between Iran-backed rebels and the beleaguered Saudi-backed government to take advantage of the growing chaos.

The United States considers it to be the extremist group's deadliest global franchise and regularly targets its militants with drone strikes on Yemeni territory.