US President Barack Obama on Monday weighed in on the row created by Internal Revenue Service ( IRS), vowing those responsible for targeting conservative political groups for extra scrutiny would be "held accountable."

Obama made the comments during a White House press conference, saying "I've got not patience with it. I will not tolerate it, and we will make sure that we find out exactly what happened on this."

Obama was referring to revelation that IRS employees at an Ohio office had flagged groups with "patriot" or "Tea Party" for additional reviews during last year's elections to see if they violated their tax-exempt status. Republicans were outraged.

Obama said he first learned of the matter on the news, and called such conduct "outrageous."

"There's no place for it, and they have to be held fully accountable," said Obama.

"You don't want the IRS ever being perceived to be biased and anything less than neutral in terms of how they operate," said Obama. "So, this is something that I think people are -- are properly concerned about."

The administration is already conducting an investigation of the matter.