U.S. army Gen. David Petraeus, the new commander of U.S. forces in Iraq, speaks during a news conference in Baghdad, Iraq. Petraeus said Thursday that insurgents in Iraq have sought to intensify attacks during a Baghdad security crackdown, and additional U.S. forces will be sent to areas outside the capital where militant groups are regrouping.

Baghdad, Iraq ? U.S. and Iraqi troops captured eight suspected insurgents Thursday in raids north of Baghdad as part of a campaign to prevent insurgents from regrouping outside the city during the ongoing security crackdown.

The operation took place in Duluiyah and the Jabouri peninsula – a bend in the Tigris River about 55 miles north of Baghdad – part of the Sunni areas around Baghdad where insurgents have fled since the crackdown in the capital began last month.

The top U.S. commander in Iraq, Gen. David Petraeus, said the security operation would be extended beyond the city limits to target these areas, which he referred to as “the Baghdad belt.”

“The priority clearly is Baghdad, (but) anyone who knows about security in Baghdad knows you must also secure the ‘Baghdad belts’ – in other words the areas that surround Baghdad,” Petraeus told reporters at his first news conference since taking command last month.

Petraeus declined to specify how long the security operation would last but said it would continue as long as necessary “to achieve its desired effect.”

“We are still in the early days of this endeavor – an endeavor that will take months, not weeks, to fully implement,” Petraeus said.

He also said he had not decided whether to ask for additional troops beyond the 21,500 combat forces already earmarked for Baghdad. The last of the reinforcements are due in early June, he said.

The New York Times reported that the operational commander, Lt. Gen. Raymond Odierno, recommended that the extra troops remain here until February. Odierno said the extra troops are needed to allow time to win over the Iraqi populace.

“We’re some months from saying, ‘OK, let’s continue at this level’ or determine what else we might do,” Petraeus said. He said he had asked Odierno “to lay out options because it’s something we want to consider early before it’s staring us in the face.”

“We’ve done that, but I certainly have not reached a conclusion,” he added. “It needs to be sustained well beyond the summer, but we’ll have to see.”

Despite the general’s cautious tone, Baghdad was relatively quiet Thursday. Police reported finding 10 bodies with signs of torture – presumably victims of Sunni-Shiite reprisal killings. That figure was well down from the 40 to 50 bodies found each day before the operation began.

Three mortar shells exploded in the Baghdad International Airport compound, breaking windows at the headquarters of Iraqi Airways but causing no casualties, witnesses said.

To the south, Shiite pilgrims continued their trek to the holy city of Karbala, where rituals were to begin today to mark the end of a 40-day mourning period after the anniversary of the death of the Prophet Muhammad’s grandson. Millions were expected to attend the weekend observance.

There were no major attacks on pilgrims Thursday, but more than 340 people have been killed across Iraq this week, mostly in assaults on Shiite pilgrims. Pilgrims will mark the 40th day of mourning for the death of Imam Hussein, grandson of the Prophet Muhammad.

Hussein’s death in battle near Karbala in the seventh century cemented the rift between Sunnis and Shiites.

Iraqi forces have set up checkpoints on roads leading into Karbala, 50 miles south of Baghdad, and at least 10,000 policemen have been deployed to the city, Iraqi officials said.