A suicide car bomb packed with explosives, mortars and rockets exploded Monday outside a U.S. base in the northern city of Mosul, killing three Iraqis — including a child — and injuring three U.S. soldiers.

Also, militants announced they were holding four new hostages but freed a senior Egyptian diplomat, amid their escalating campaign to force U.S.-allied countries and foreign contractors to flee Iraq. In other violence, an Iraqi government official was gunned down by assassins outside his Baghdad home.

Suicide attacks, assassinations, roadside bombs and abductions have been persistent tactics in the 15-month insurgency sowing chaos across Iraq. Kidnappings have escalated, however, since the Philippines (search) last week met militant demands and withdrew troops to save the life of a Filipino truck driver.

Egyptian Mohammed Mamdouh Helmi Qutb (search) — the militants' highest-ranking captive — was abducted three days ago. His kidnapping was followed by censure from leaders in Iraq and the Arab world for excesses including beheadings, and it was possible the criticism factored in the diplomat's swift release.

An Egyptian Foreign Ministry official said Qutb was released after negotiations and was in good condition at the mission's headquarters. His captors said in a statement on the pan-Arab television station Al-Jazerra that they had decided to free Qutb because he was a good religious man and had good morals.

Militants said they had taken the diplomat to deter Egypt from sending security experts to help the new Iraq government, and his abduction seemed to signal that insurgents were seeking higher-value targets.

Many of the more than 70 people abducted in Iraq have been truck drivers, more vulnerable than heavily armed military troops as they bring essential goods and materials into the country.

Since Filipino truck driver Angelo dela Cruz (search) was freed Tuesday, separate militant groups have kidnapped three Kenyans, three Indians and one Egyptian working for a Kuwaiti company. Two different groups announced Monday they were holding two Pakistanis and two Jordanians, and threatened to kill them if their companies continue working in Iraq.

"We've seen since the Philippines government acceded to the demands of the terrorists a whole spate of new hostage taking," Australian Foreign Minister Alexander Downer said. "And I'm afraid that's what inevitably is going to happen in those circumstances."

George Sada, spokesman for Iraqi interim Prime Minister Ayad Allawi, also expressed regret at the Philippines' decision: "We think that to bow to the terrorists' threats is the wrong policy."

Iraqi government officials say the abductions are damaging reconstruction efforts, and foreign companies — particularly transport firms — say kidnappings have driven up the cost of doing business and made it tougher to find employees.

Adel Abou Hawili, shipping manager for a Kuwaiti company, said kidnappings have forced transport costs up "50 to 65 percent" and made it harder to find drivers to work here. The lack of security has forced the company to subcontract land transport jobs to Iraqis to "avoid the risks."

Early Tuesday, a mortar shell struck the residential Salhiya district in central Baghdad, killing at least one Iraqi civilian and injuring another, an Associated Press Television News cameraman at the scene said.

In the Mosul bombing, a suicide attacker detonated the explosives-packed Chevrolet about 50 yards from the gate of the U.S. base. Three Iraqis standing nearby, a woman, a child and a guard, were killed, and three U.S. soldiers and two other Iraqi guards were wounded, said U.S. military spokeswoman Capt. Angela M. Bowman.

"Four cars were totally burned," said base employee Sami Omar. "I saw two people lying on the ground."

Mosul has been the scene of numerous terrorist attacks. The last major one was June 24, when insurgents blew up four car bombs, killing more than 60 people, the military said.

Militants also have targeted Iraqi government officials and civilians working for U.S. or Iraqi forces, calling them traitors or collaborators.

In Baghdad, gunmen killed Col. Musab al-Awadi, the Interior Ministry's deputy chief of tribal affairs, and two of his guards, according to Sabah Kadhim, an Interior Ministry spokesman.

During Saddam Hussein's regime, Al-Awadi had been forced to retire from the police force in 1979 because of his connection to the opposition Shiite Dawa party. He was appointed to his new post after Saddam's ouster, said Col. Adnan Abdel Rahman, another spokesman for the ministry.

Also Monday, gunmen in the southern city of Basra killed two Iraqi women who were working as cleaners with British forces, police Lt. Col. Ali Kadhem said. Two other women were seriously wounded.

In the latest kidnappings, a group calling itself the Islamic Army in Iraq released a video Monday announcing it had abducted two Pakistanis and passed a death sentence against them in part because of Pakistani President Gen. Pervez Musharraf's statements about the possibility of sending troops to Iraq.

The group did not say when it would kill the men.

The Pakistani government had declared the two men, Raja Azad, 49, an engineer, and Sajad Naeem, 29, a driver, missing over the weekend.

The video aired on Al-Jazeera briefly showed the two men, along with some of their identity cards, and an Iraqi contract driver whom they did not threaten.

The men reportedly work for the Kuwait-based al-Tamimi group; the militants also warned the firm to stop doing business in Iraq or it would kill more of its employees.

In a separate abduction, a group calling itself the Mujahedeen Corps, announced it was holding two Jordanian drivers and demanded their Jordanian company stop cooperating with U.S. forces and cease doing business here or they would kill the hostages in 72 hours.

If the company does not comply "it will bear the consequences of the killing and retribution against these two men," one of the militants said on the video obtained by Associated Press Television News.

The video showed the drivers, identified as Fayez Saad al-Udwan and Ahmed Salama Hassan, seated on the floor, while six masked militants, carrying a variety of weapons including a sword, stood behind them.

Other video footage released Monday showed a third group of kidnappers — the one holding the Indians, Kenyans and Egyptian. It said it was extending its deadline for killing the seven men but did not say by how long.