Attacks against U.S. troops have increased following a call earlier this month from Al Qaeda in Iraq's leader to target American forces, the top U.S. military spokesman said Wednesday.

Maj. Gen. William B. Caldwell also said Iraqi and American troops were expecting violence to increase further during the Islamic holy month of Ramadan, which begins next week. He said where the military usually has two to five battalion-level operations going on at any given time across the country, there were now 10 ongoing in preparation.

"As we all know, historically Ramadan has been a period of increased violence," Caldwell said.

It was a particularly deadly two-day period, with more than 50 killings throughout the country including a suicide truck bombing at an Iraqi police headquarters in Baghdad, which razed the building and killed at least seven people.

Caldwell said attacks against U.S. troops were mostly carried out by suicide car bombers or roadside bombs. He added that the number of "execution style" killings by death squads also had increased in the past week.

The rise in attacks against American forces came after a threat issued Sept. 7 by Abu Ayyoub al-Masri, also known as Abu Hamza al-Muhajer, who took leadership of Iraq's most feared terror group after Abu Musab al-Zarqawi was killed in a June 7 airstrike north of Baghdad. The U.S. military has put a $5 million bounty on his head.

In an audio Internet message, he threatened new attacks against U.S. forces and their Iraqi allies and addressed Al Qaeda leader Usama bin Laden, saying, "We are still sticking to our obligation."

"The fire in our blood will never cool, and the swords that have been colored with your blood are still thirsty for more of your rotten heads," he said on the 20-minute tape, addressing the Americans and their allies.

He urged his followers "not to rest until each one of you kill at least one American within the next 15 days, by a sniper bullet, spear, explosive or martyrdom car."

Caldwell said he also expected to see the month of Ramadan bring more foreign extremists into action against U.S. forces.

"We do anticipate seeing an increase of foreign fighters killed or captured in September," Caldwell said, adding militants captured in the past have come from 25 countries, primarily Egypt, Syria, Sudan and Saudi Arabia.

The military said Wednesday that an American soldier was killed by a roadside blast northeast of Baghdad the day before.

The news came after the U.S. military announced the deaths of four other soldiers in Iraq. One was killed Tuesday by a suicide car bombing, which also wounded two other soldiers. Another two soldiers were killed Sunday — one by small arms fire and the other by a roadside bomb in Baghdad. A fourth soldier, assigned to a medical task force, died Monday of non-combat related injuries in the capital while a fifth died Wednesday in what the military called a "non combat incident."

Also Wednesday, a civilian was killed and two more wounded in east Baghdad in a roadside bombing targeting an American convoy just before noon, police Capt. Mohammed Abdul-Ghani said. There were no immediate reports of American injuries.

Another roadside bombing targeting a patrol in the capital's al-Khadhra suburb wounded a policeman and two civilians, police said.

The deadly suicide truck bomb attack came in the southern Baghdad neighborhood of Dora, one of those recently swept by the military in the neighborhood by neighborhood security crackdown dubbed "Operation Together Forward."

The bomb hit as policemen were coming on duty, killing the seven and injuring 14 others, said Capt. Jamil Hussein.

In other violence, police in the northern city of Mosul confirmed that tandem bombings killed 21 people near the northern city and wounded 50 others.

A parked car bomb detonated near an Iraqi army base in Sharqat, about 45 miles south of Mosul, on Tuesday night, and a suicide bomber detonated his explosives as a crowd gathered at the scene of the first bombing, police said.

Another policeman was killed when a mortar round landed near a patrol in northern Baghdad, police Lt. Bilal Majid said. Two civilians were also wounded in the attack in the Waziriya neighborhood, Majid said.

One Iraqi soldier was killed and two others wounded in an attack on an Iraqi army checkpoint in the Yarmook district in western Iraq while another two Iraqi soldiers were killed and one wounded in an attack on a checkpoint in the Balad Ruz area, northeast of Baghdad, police said.

Another 12 civilians were injured in a series of three roadside bombings aimed at police patrols Wednesday in the Hillah area, about 60 miles south of Baghdad, police Lt. Osama Ahmed said. No police were reported injured.

Already, attacks around Iraq on Tuesday killed at least 16 Iraqis and injured 55 others.

In other killings reported Wednesday, the mutilated body of a policeman was turned in to the morgue in Kut, about 100 miles southeast of Baghdad, after being found in the al-Falahiya district east of the city in the morning.

The body of Mahmoud Hassan Mohammed was found blindfolded with his arms and legs cuffed, and he was shot in various place and showed signs of torture, morgue official Mamoun Ajeel Al-Rubai'ey said.

The body of an unknown civilian in a similar condition also was turned in to the morgue after being dragged out of the Tigris River about 30 miles south of Baghdad, Al-Rubai'ey said. An unknown victim in a sack was also pulled out of a river in the northeastern Diyala province, police said.

Two policemen and a civilian were also wounded in a bomb blast in Diyala that targeted a police patrol, police said.

Nearly 200 bodies of Iraqis who had been tortured and shot have turned up around Baghdad in the past week, including three found Tuesday in an eastern section of the capital.

Most are found bound and blindfolded, apparent victims of sectarian violence. Both Shiite and Sunni lawmakers called Tuesday for the defense and interior ministers to take steps to stop the death squads.