GUATEMALA CITY (Reuters) - Thousands gathered in the main square of Guatemala's capital on Saturday to protest against corruption after a wave of graft scandals prompted a Cabinet shake-up and the resignation of the vice president.

Many of the demonstrators' placards called for President Otto Perez to also step down; others urged a crackdown on political corruption and crime - demands echoed in similar protests in other Guatemalan cities.

"We don't want Otto Perez in power any more," said dentist Otto Chojolan amid the crowd in Constitution Square. "They've stolen so much money, and that's why I've come to protest - it's important the politicians know we are unhappy."

Anti-corruption protests have grown in recent weeks as arrests of officials for graft drove Perez last week to dismiss the interior, energy and environment ministers and the country's intelligence chief among other senior officials.

The day before the reshuffle, Guatemala's central bank chief Julio Suarez and 14 other people were arrested, accused of rigging a multi-million dollar contract from the country's Social Security Institute in favor of a pharmaceutical firm.

And earlier in May, Vice President Roxana Baldetti stepped down after accusations that she had been linked to a ring accused of taking bribes to avoid customs taxes.

The corruption scandals have buffeted Perez's conservative Patriot Party ahead of presidential elections in September. Perez is barred from re-election, but he has repeatedly said he will not step before the end of his term.

(Reporting by Sofia Menchu; Writing by Gabriel Stargardter; Editing by W Simon)