Nigeria's House of Representatives speaker has threatened to order the arrest of the central bank chief and 14 others over the fate of $8bn (£5bn).The office of speaker Aminu Tambuwal said he had signed arrest warrants for Lamido Sanusi and the other officials.The warrants will be executed if they fail to appear before MPs to explain the whereabouts of money allegedly owed to the treasury, a spokesman said.Mr Sanusi said he was unaware of the warrant and denied any wrongdoing.He is widely respected in banking circles in Africa and the West. In 2011, he was named the Central Bank Governor of the Year by the global financial publication, The Banker.'Nothing personal'Earlier this month, he called for the size of the House of Representatives, the 360-member lower chamber, to be reduced to free up money for development.He also called for the number of public servants to be cut by half.Mr Tambuwal's spokesman, Imam Imam, said other officials for whom warrants have been issued include Andrew Yakub, group managing director of the state-owned Nigeria National Petroleum Corporation's (NNPC), and National Pension Commission Director-General Muhammad Ahmad.He said MPs would enforce the arrest warrants if the officials failed to appear before a parliamentary committee to account for the money.The officials apparently have until Thursday to appear before MPs, reports the BBC's Chris Ewokor from the capital, Abuja.The warrants were issued because the 15 officials are accused of refusing to honour several invitations to explain to MPs the alleged failure to transfer about $8bn to the treasury, he says.However, a police spokesman told our correspondent he had no knowledge of the warrants.Mr Sanusi told the BBC he was out of Nigeria, but the deputy governor would appear before MPs.He said he was unaware of an arrest warrant for him."I personally don't believe the speaker signed such a warrant as these things are not personal," he said.Mr Sanusi said the Central Bank of Nigeria has made remittances to the treasury in accordance with the law."Our accounts are audited by two reputable external auditors... No government agency or department even comes near our contribution to the budget," he said.Nigeria is Africa's biggest oil producer, but most of its population lives in poverty.Critics say corruption is endemic in the government and there is a lack of financial accountability.