A senior U.S. military official in Iraq says the recent escalation in insurgent attacks may be attributed to a meeting last month of top insurgent leaders held in neighboring Syria.

The official told reporters Wednesday that during the meeting of Abu Musab al-Zarqawi's top lieutenants, orders were given to use more car bombs in daily operations. This month in Baghdad alone there have been 21 car bombings - a significant increase.

Since a U.S. Marine-led offensive against insurgents in western Iraq last week, there has been a visible decrease in insurgent attacks.

But there has been some violence. Wednesday, a top general in the interior ministry, Ibrahim Khamas was killed in a drive-by shooting. There also were attacks in Baquba, Mosul and Baghdad that killed and wounded several people.

And the influential Association of Sunni Clerics publicly accused the militia of the main Shi'ite political party of killing Sunni clerics. A senior militia official denied the charge and said the Sunnis are trying to incite sectarian strife.

Some information for this report provided by AP and Reuters.