(Adds conflicting reports over attack)

TAL AFAR, Iraq, April 27 (Reuters) - Senior Iraqi security officials on Friday denied there had been a suicide car bombing in northern Iraq on Friday.

Earlier, a police source had said the car bomb had targeted an Iraqi army checkpoint between the town of Tal Afar and the city of Mosul and had killed and wounded dozens of people.

Another police source had confirmed the attack but had no information on casualties.

But senior Iraqi security officials and the mayor of Tal Afar said there had been no bombing in that area on Friday.

A nine-week-old U.S.-backed security crackdown in Baghdad has prompted some insurgents to leave the capital and step up attacks elsewhere in Iraq, raising overall civilian deaths in the country.

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