The U.S. military reports six American soldiers were killed Wednesday in a bobby-trapped house during a new operation in northern Iraq. The joint U.S.-Iraqi offensive was launched Tuesday against al-Qaida in the north, including the most violent Diyala province. VOA's Deborah reports from Baghdad.

More than 70,000 U.S. and Iraqi troops are in their second day of operation against al-Qaida in northern part of Iraq. At a news conference in Baghdad, the U.S. commander for northern Iraq, Major-General Michael Hertling, said it will be a challenge. "The people that left Anbar and Baghdad have moved up into my area," he said.

Hertling said the offensive is focused in volatile Diyala province especially the agricultural city of Muqdadiyah. When a brigade of five-thousand U.S. troops and a division of Iraqis launched attacks near Muqdadiyah, Hertling said they encountered less opposition than expected.

U.S. military officials say coalition forces detained six suspects on Wednesday.

Hertling said additional forces are being sent to the four northern provinces but he would not say how many. He only said more troops are needed in Diyala. "It was also a province that didn't see a lot of forces insuring stability over the long haul. There would be forces that would go in and then come out," he said.

Hertling also spoke about what he called "spectacular attacks" by Al-Qaida in northern Iraq and other parts of the country. He said these mostly large-scale suicide bombings have increased recently. "While we have seen a reduction in the number of attacks in most areas of Iraq, and to a lesser degree in northern Iraq, there has been a marked increase in AQI (Al-Qaida) activity in Diyala province in the form of high-profile, spectacular events. This does not mean an increase in attacks, but it does mean an increase in these kinds of high profile attacks," he said.

Hertling said some of these attacks have targeted volunteer security patrols, also known as concerned local citizens, who are paid to guard their communities. He said five severed heads had been found on a road in Diyala with warnings in Arabic written in blood on their foreheads that all volunteers would share their fate. Despite these warnings, he said the movement is growing.

"We have about 15,000, a little less, concerned local citizens who are standing up to help the Iraqi security forces because they are sick of the violence."

Hertling said as the suicide attacks continue to kill innocent people, more people will turn against al-Qaida.