By Stanley Carvalho

ABU DHABI (Reuters) - The rise and fall of Abu Dhabi tycoon Khadem al-Qubaisi, named this week in U.S. Justice Department lawsuits seeking to seize over $1 billion in assets, illustrates the unpredictability of an opaque Gulf business world fueled by huge sums of oil money.

In a few years, Qubaisi rose from obscurity to become one of the top executives in the United Arab Emirates by taking the helm of International Petroleum Investment Co (IPIC), a state-run company investing some of Abu Dhabi's petrodollars.

His fall was even faster. In April last year he was abruptly replaced as managing director of IPIC, and in subsequent months he resigned from a string of management positions and board memberships at other companies around the UAE and the region.

Neither Qubaisi nor the companies involved gave any public explanation for his departure, and his current whereabouts are not publicly known. Attempts by Reuters to contact him or his lawyers were unsuccessful, while IPIC declined to comment.

Some members of Abu Dhabi's business community believe he fell out of favor with top officials of the emirate because he became too flamboyant, in a society where many of the richest and most powerful people keep low profiles.

“He was bold, brazen, aggressive and to an extent an achiever, but he was also flashy and flamboyant, which was at variance with the top brass of Abu Dhabi,” one executive who knew Qubaisi told Reuters, speaking on condition of anonymity because of the sensitivity of the matter.

“His flamboyance was tolerated until things got out of hand and it became an embarrassment."

Civil suits filed in U.S. federal court on Wednesday aim to seize over $1 billion in assets which U.S. prosecutors say were tied to money stolen from Malaysian sovereign wealth fund 1MDB, which established close ties with IPIC during Qubaisi's tenure.

Qubaisi and several other people and institutions named in the suits, including another former Abu Dhabi executive, Mohammed Ahmed Badawy Al-Husseiny, have not been charged with crimes.

But the suits allege Qubaisi received proceeds from 2012 bond sales by 1MDB "for his own personal benefit", violating the terms of his post as managing director of IPIC. The U.S. government is claiming the right to seize assets including luxury properties in New York and California, Monet and Van Gogh paintings, and a Bombardier jet.

SPECTACULAR

Born in 1971, Qubaisi attended high school in Abu Dhabi and studied at a UAE university, obtaining a bachelor’s degree in economics in 1993, according to people familiar with him.

In the same year he joined the Abu Dhabi Investment Authority (ADIA), now one of the richest sovereign funds in the world. He rose to become a senior financial analyst in ADIA's North American equities department and in 2000 moved to IPIC as an investment manager.

It was after he was appointed IPIC's managing director in May 2007 that Qubaisi engineered his most spectacular deals. IPIC bought a majority stake in Aabar Investments, a local holding company, and embarked on a string of high-profile investments across the globe, including stakes in German carmaker Daimler AG, space tourism firm Virgin Galactic, and Spain's Banco Santander.

Qubaisi raised IPIC's international profile by publicizing his successes, and hit back at critics. Questioned about his deals by a Reuters reporter two years ago, he replied: “Remember, I am a boxer. If anyone plays around with me, I can squash them like a mosquito."

But after the global financial crisis hit the UAE in 2009, signs of strain began to emerge in Qubaisi's business empire. Aabar borrowed aggressively but then suffered losses as investments turned sour.

Meanwhile, Qubaisi left IPIC heavily exposed to 1MDB when the Abu Dhabi company guaranteed $3.5 billion of the Malaysian fund's bonds in 2012. This became an embarrassment for Abu Dhabi when big losses at 1MDB were disclosed in early 2015.

IPIC is now trying to claw back its money; last month it claimed $6.5 billion from 1MDB and Malaysia's government in a case which it submitted to the London Court of International Arbitration. Another Abu Dhabi state fund, Mubadala, said it would bolster IPIC's finances by merging with it.

Qubaisi, meanwhile, has been under investigation by UAE as well as U.S. authorities. In April, financial sources said the UAE central bank had told banks to freeze the assets of Qubaisi and Husseiny and provide information about their deposits and transactions. The central bank and other Abu Dhabi officials did not respond to queries on the nature of the probe.

(Editing by Andrew Torchia; editing by Peter Graff)