Updated

American forces are tracking about 50 members of an elite Iranian force who have crossed the border into southern Iraq to train Shiite militia fighters, a top U.S. general said Sunday.

In east Baghdad, a mortar barrage slammed into a mainly Shiite neighborhood, killing 12 and wounding 31, police said, and a major battle raged north of the capital where residents of a Shiite city were fighting what police said was a band of Al-Qaeda in Iraq gunmen.

Maj. Gen. Rick Lynch, whose command includes the volatile southern rim of Baghdad and districts to the south, said his troops are tracking about 50 members of Iran's Revolutionary Guard Corps in their area — the first detailed allegation that Iranians have been training fighters within Iraq's borders.

"We know they're here and we target them as well," he said, citing intelligence reports as evidence of their presence.

He declined to be more specific and said no Iranian forces have been arrested in his territory.

"We've got about 50 of those," he said, referring to the Iranian forces. "They go back and forth. There's a porous border."

The military has stepped up allegations against Iran in recent weeks, saying it supplies militants with arms and training to attack U.S. forces.

Iran denies the allegations and says it supports efforts to stop the violence.

The Bush administration is moving toward blacklisting Iran's Revolutionary Guard Corps as a "terrorist" organization, subjecting at least part of the entity to financial sanctions, U.S. officials said this week.

A decision has been made in principle to name elements of the corps a "specially designated global terrorist" group, but internal discussions continue over whether it should cover the entire unit or only the Guard's Al-Quds force, the most elite and covert of Iran's military branches, which has equipped and trained Muslim fighters outside Iran's borders.

Lynch, whose mission is to block the flow of weapons and fighters into the Baghdad area, said Sunni and Shiite extremists have become increasingly aggressive this month, trying to influence the debate in Washington before a pivotal progress report on Iraq.

He singled out the Shiite extremists as being behind rising attacks using armor-piercing explosively formed penetrators, or EFPs, which he said were largely assembled in Iraq from parts smuggled in from Iran. He also noted a marked increase in Iranian-rockets that have been increasingly effective against U.S. bases.

There has been an overall decrease in attacks against U.S. and Iraqi forces, as well as civilians, south of Baghdad, but 46 percent of those were being carried out by Shiite extremists, Lynch said.

"The real difference now is we've got to spend as much time fighting the Shia extremists as Sunni extremists," he said.

Women and children were among the 12 victims of the mortar attack in eastern Baghdad. Some houses in the neighborhood were damaged, according to police, and witnesses said U.S. helicopters were hovering above the attack site.

Hussein Saadon, 56, an owner of a small minibus station, was soaked in blood after he drove four victims to the hospital. He said the district had been without electricity for several days and the people were suffering in the heat.

"It fills me with pain and anger to see an attack on such poor area where is no presence of police nor army bases or checkpoints," Saadon said.

In Khalis, 50 miles north of Baghdad, police said more than 1,500 people including sheiks and dignitaries had gathered near city hall to launch the counteroffensive against al-Qaida fighters who have been regularly firing mortars into the town and kidnapping residents at illegal checkpoints. Police said five townspeople were killed in the early hours of the fighting.

At least seven people were killed and 18 wounded in a mortar attack on Khalis on Saturday.

Police said members of the city militia also said they were determined to push al-Qaida fighters out of the nearby town of Hibhib, where the terror organization's former leader Abu Musab al-Zarqawi was killed in an U.S. air strike.

In central Baghdad, gunmen driving several cars waylaid a minibus headed for Sadr City, the capital's Shiite enclave, and abducted 15 passengers, police said.