CHICAGO -- An old friend and fundraiser of US Democratic presidential hopeful Barack Obama was Wednesday found guilty of fraud for using his political clout to demand kickbacks and win government contracts.

Real estate developer Antoin "Tony" Rezko was also convicted of bribery and money-laundering in the case which has dogged Obama during his quest to secure the party's presidential nomination, even though he is not accused of any wrong-doing.

In all, jurors found Rezko guilty of 12 counts of fraud, two of aiding and abetting bribery and two of money laundering after deliberating for several weeks.

He was cleared on eight other charges in the verdict which came a day after Obama clinched enough delegates to be the Democratic party's presidential nominee to stand in the November elections.

The Illinois senator subsequently donated all the money raised for his White House bid by Rezko to charity, but prosecutors have said some of the kickbacks ended up in his campaign coffers.

Wednesday's verdict was immediate fodder for Obama's Republican rival John McCain, with the Republican Party's national committee sending out a statement saying "Obama has maintained a friendship with a now convicted felon."

Billing its attack as a research briefing and editing it like a fact sheet, the Republican statement was a series of newspaper clippings referring to the case, which alleged that ties between the two men deepened over 20 years despite "ample warnings of Rezko's corrupt behavior."

Obama has already come under fire for a 2005 land deal with Rezko when it was widely known that the developer was under federal scrutiny, something the senator later called a "boneheaded" move.

Prosecutors accused Rezko of "using his power and influence to benefit himself and his friends."

Rezko, who was the second largest fundraiser and a key advisor to Illinois Governor Rod Blagojevich, was accused of pulling the strings in a corrupt scheme of pay-to-play politics.

He used his influence and power to trade state jobs and lucrative contracts for campaign contributions and hundreds of thousands of dollars in kickbacks, prosecutors said.

But Rezko's defense team said the government's case rested entirely on the unreliable testimony of a drug-addicted con man, Stuart Levine, who lied to save his own skin when the FBI caught wind of his schemes.

Blagojevich, a Democrat, has not been charged with participating in the scheme and denies any wrongdoing.

Rezko did not take the stand during the trial which started March 3 and his defense team did not call any witnesses.