BAGHDAD - Iraq's defense minister promised yesterday to wage a new crackdown in a volatile province northeast of Baghdad where militants are trying to regroup after being routed from their urban stronghold there last summer.

Suicide attacks have killed more than 20 people in the last three days in Diyala province, a tribal patchwork of Sunni Arabs, Shiites and Kurds that stretches from Baghdad to the border with Iran.

Defense Minister Abdul-Qader al-Obeidi told the Associated Press that preparations had begun for a fresh military operation in the provincial capital, Baqubah, about 35 miles from Baghdad.

"If we succeed in controlling areas of Diyala close to Baghdad, the rate of incidents in Baghdad decreases by 95 percent," al-Obeidi told the Associated Press.

British Prime Minister Gordon Brown, meanwhile, arrived in southern Iraq on a surprise visit to the southern city of Basra, signaling what London hopes will be the transition from a military mission in Iraq to one with a stronger economic component, aimed at reinvigorating a country torn apart by war and years of neglect under Saddam Hussein.

"The great venture that started with all the difficulties we face, that cost casualties, means we have managed now to get Iraq into a far better position," Brown told British troops, who lined the staircases of an airport base to watch his evening arrival."

The British plan to hand over security responsibilities for the oil-rich area to the Iraqis in the coming weeks.

Although violence has declined sharply in Iraq since June, it has been a constant challenge to subdue extremists in Diyala, which is the eastern gateway to Baghdad.

Al-Qaeda in Iraq began moving into Diyala in 2006 after losing its sanctuaries in Anbar province. Last summer, American troops regained control of Baqubah in a pair of operations, restoring some government services and commerce after months of isolation.

But U.S. officers said at the time they expected the extremists to scatter to hills north of Baqubah and to the city of Muqdadiyah to the east and try to regroup.

Rear Adm. Gregory Smith, a U.S. military spokesman, credited intelligence gleaned from Iraqis tired of militant violence as among the factors that have led to a decline in violence around the country. He said Diyala would soon see the same level of improvement.

"We believe there will be a secure, stable Diyala in months to come," Smith said.