Three members of Iraq's largest Sunni Arab political party were kidnapped and killed Friday on a Mosul street in broad daylight.

A spokesman for the Iraqi Islamic Party said the men were hanging posters urging people to vote in October's scheduled constitutional referendum when they were abducted. They were driven to a different part of the city, made to stand against a wall in front of a mosque and then sprayed with gunfire.

Some insurgent groups have threatened to kill anyone who participates in the constitutional referendum.

Meanwhile, in Baghdad, hundreds of supporters of radical Shi'ite cleric Moqtada al-Sadr demonstrated against calls for federalism in Iraq.

Shi'ites are divided over the issue. Iraq's largest Shi'ite party, the Supreme Council for the Islamic Revolution in Iraq supports it, but several smaller groups do not.