HARARE (Reuters) - A Zimbabwean court on Friday charged a top official of a war veterans' group with insulting President Robert Mugabe after former independence fighters accused the aging leader of ruining the once-promising economy.

Douglas Mahiya, information secretary of the Zimbabwe National Liberation War Veterans Association (ZNLWVA), appeared at the magistrates' court in handcuffs and was charged with undermining or insulting the authority of the president.

The government has denounced the statement last week by the veterans, once among Mugabe's staunchest supporters, as "treasonous". Mahiya, who was not asked to plead, faces up to a year in jail if found guilty.

The insult law has been challenged at the Constitutional Court by dozens of activists, but the court is still to rule on whether the legislation limits individual freedoms.

Harare magistrate Vakayi Chikwekwete said he would hear Mahiya's bail application on Saturday and ordered the state to investigate the ZNLWVA official's claim that he was verbally abused by police while in custody.

Mugabe, now 92 and looking increasingly frail, faces growing opposition even from his own ZANU-PF party over his plans to contest the 2018 presidential vote.

(Reporting by MacDonald Dzirutwe; Editing by Tom Heneghan)