El Salvador's president Nayib Bukele, a self-described 'cool dictator', has stepped up arrests of critics. (AFP pic)SAN SALVADOR: El Salvador sentenced rights activist Fidel Zavala on Tuesday to 15 years in prison, drawing criticism from campaign groups.

Zavala is one of more than 20 leaders from the UNIDEHC rights group arrested in February last year on charges related to the fraudulent sale of real-estate plots.

President Nayib Bukele, a self-described "cool dictator" who has locked up more than 90,000 suspected gang members in a sweeping crackdown, has also stepped up arrests of critics.

Rights groups have decried arbitrary arrests and torture in custody.