By Deisy Buitrago and Girish Gupta

CARACAS, July 2 (Reuters) - Venezuela's President Nicolas Maduro raised the country's minimum wage by half on Sunday to just over $12.50 per month at the black market exchange rate.

But given the currency's fall, the new minimum monthly wage of 97,532 bolivars is effectively down 17 percent in dollar terms since the last increase in May.

The currency's fall -- of 99.7 percent since Maduro was elected president in April 2013 -- has exacerbated a brutal economic crisis that has millions struggling to find or afford food.

A thousand dollars bought in local currency when Maduro was elected would be worth just $3 today.

Maduro's leftist government blames speculators and the opposition for the problems.

"Following the immoral campaign that fixes prices through a false dollar abroad ... we are going to put the handcuffs on ... the whole campaign of speculation," said Maduro on state television, adding that the rise would be effective retroactively from July 1.

The monthly salary is accompanied by a food ticket, the value of which also went up to 153,000 bolivars per month --bringing the total to just over $30 a month at the black market rate.

Maduro often describes the salary increases as a "world record," while critics see it as a stark indicator of economic mismanagement.

Street unrest across the country has left more than 80 people dead in three months. (Writing by Girish Gupta; Editing by Sandra Maler)