The top US commander in Iraq, Gen. David Petraeus, has accused Iran and Syria of supporting insurgents and foreign fighters in Iraq.

"We are concerned very much about the lethal accelerants, as they are called, that do come from Iran," he said in Baghdad on Wednesday.

"And the same way we do about what comes through Syria." CNN quoted Petraeus as saying.

The general's comments on Iran comes just one day after Sen. John McCain, R-Arizona, in a press conference in Jordan accused Iran of training Iraqi extremists in Iran and sending them back to Iraq.

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McCain also expressed concern about a large cache of explosives found in Iraq and hinted that they may have been sent from Iran.

Iran strongly denies any meddling in Iraq's internal affairs and has voiced its support for establishing peace and security in its neighboring country.