BAQUBAH, IRAQ - Sunni insurgents have been streaming out of Baghdad to escape the security crackdown, carrying the fight to neighboring Diyala province, where direct fire attacks on Americans have nearly doubled since last summer, U.S. soldiers say.

That has led to sharp fighting only 35 miles north of the capital in a province known as "Little Iraq" because of its near-equal mix of Sunni and Shiite Arabs as well as Kurds -- the country's three major groups. At stake is a region that extends from the northeastern gates of Baghdad to the border with Iran.

"I was here in 2004, and I don't remember them ever attacking tanks in open daylight, but now that's exactly what they're doing," said Capt. Paul Carlock, 31, of Chattanooga, Tenn., a company commander in the Army's 1st Battalion, 12th Cavalry Regiment. "There's a big Sunni influx here, and in the last month or so it's been pretty violent. They're getting more aggressive and changing tactics."

Some U.S. officers suspect the publicity for the Baghdad security plan may have encouraged extremists, both Sunnis and Shiites, to flee the capital for surrounding provinces, including Diyala, where fewer U.S. troops are stationed.

On Thursday, a rooftop sniper fired on members of the 12th Cavalry as they patrolled a suburb of Baqubah with Iraqi soldiers. Shots rang out through abandoned streets for about 15 minutes until a Bradley fighting vehicle rumbled in, firing a 25 mm machine gun that thundered through the neighborhood and drove off the attackers.

It is unclear how many insurgents have entered the province over the past month. But U.S. officers think the numbers must be large because of the increase in violence.

In July, U.S. soldiers came under 90 direct fire attacks -- meaning weapons aimed straight at them. Last month, the number of such attacks was up more than 70 percent, to 157, according to Col. David W. Sutherland, commander of the 1st Cavalry Division's 3rd Brigade.

Lt. Col. Morris Goins, 41, of Southern Pines, N.C., a battalion commander, said the surge in attacks was a result also of more aggressive U.S. combat operations.

"The more you're out there, the more contact you have," said Goins, whose battalion is responsible for security in the provincial capital of Baqubah. "You've got more than 20,000 more American troops piling into Baghdad, so these insurgents are going to go somewhere."

Goins' battalion has lost 17 soldiers since it arrived in Iraq in October. Nine of them were killed in the past 11 days.

"That wears on you," Goins said. "The violence has definitely increased to a baseline where we have contact every single day."

Get $150+ in coupons in every Sunday N&O. Click here for convenient home delivery.