LIMA, July 30 (Reuters) - Peru was mired in uncertainty on Friday as bonds tumbled and the local currency weakened after newly-elected Socialist President Pedro Castillo appointed hard-left Marxist as prime minister while the key post of finance minister remained vacant. Guido Bellido was named prime minister, dimming hopes of a moderate administration. Most of the rest of the cabinet was also sworn in, but the lack of an economy czar is likely to create uncertainty in markets already rocked by a campaign in which Castillo called himself a Marxist-Leninist. Castillo, who took office on Wednesday, took to Twitter in the early hours of Friday to defend his new government. “Our cabinet belongs to the people. It answers to the people,” Castillo said on Twitter at dawn, defending his government team. “Our commitment is with Peru and with no other interest than to dedicate each and every one of our efforts to build a more just, free and dignified country. We will not disappoint your trust,” he tweeted. Castillo’s failure to appoint a finance minister exacerbated those concerns, JPMorgan said in a note. The local sol currency lost over 3% to the dollar in early trading in Lima, while Peru’s dollar bonds slid. Reporting by Marco Aquino, writing by Hugh Bronstein Editing by Marguerita Choy Our Standards: The Thomson Reuters Trust Principles.