MEXICO CITY (AFP) - The sultan of the southern Malaysian state of Johor has commuted the death sentences of three Mexican brothers who were set to be hanged for drug trafficking crimes, Mexico said.

After years of lobbying by Mexican diplomats, Sultan Ibrahim Sultan Iskandar of Johor - one of Malaysia's most powerful and wealthiest state rulers - commuted the men's death sentences to life in prison, Mexico's foreign ministry said on Thursday (Sept 20).

"This was the result of a long process and intense dialogue with Malaysian federal authorities," it said in a statement.

The brothers - Simon, Luis Alfonso and Jose Regino Gonzalez Villarreal - were arrested in a raid on a methamphetamine lab in Johor in March 2008.

The brothers, who hail from the Mexican state of Sinaloa - home to jailed drug lord Joaquin "El Chapo" Guzman's Sinaloa cartel - insisted they were innocent, saying they had been hired to clean the building and were unaware what was being made inside.

But a Malaysian court sentenced them to hang to death in May 2012.

The conviction was upheld on appeal the following year.

Mexico, which does not use capital punishment, neither accepted nor rejected the court's guilty verdict, but pushed for the death sentence to be commuted.