Iraq ? A car bomb tore through a crowded market in a Kurdish area in the disputed city of Kirkuk on Thursday, killing at least five people in the latest attack to signal rising tensions in northern Iraq.

U.S. officials have warned that disputes between minority Kurds and Arabs over oil and land threaten to erupt into a new front in the Iraq conflict while violence elsewhere declines.

The fears have taken on new urgency as the U.S. military prepares to withdraw its forces from the country by the end of 2011. Prime Minister Nouri al-Maliki, a Shiite, and Kurdish leaders met earlier this week and promised to try to overcome their differences.

Several bombings in recent weeks also have raised concern about the readiness of Iraqi forces to take over their own security more than a month after U.S. troops withdrew from urban areas as part of a plan to pull out entirely by the end of 2011.