BAGHDAD, Iraq - A senior Egyptian diplomat returned to work today, a day after being released by militants, while a Baghdad mortar barrage killed an Iraqi garbage collector and injured 14 coalition soldiers. Gunmen also killed a hospital official south of the capital.

The release of Mohammed Mamdouh Helmi Qutb, the third ranking diplomat at the Egyptian mission here, came as two different militant groups threatened to kill four new foreign hostages in an increasingly audacious wave of kidnappings in Iraq. A third group threatened attacks to cut off the highway between Jordan and Baghdad, a key supply route for the U.S. military.

As Qutb arrived at the Egyptian Embassy in Mansour, northwest of Baghdad, he thanked "all the people concerned in securing his release."

"Thanks to God, we are going to perform our work at the embassy, there is no problem," Qutb told reporters.

Four or five mortars were fired early today toward Baghdad's so-called Green Zone, the site of Iraq's interim government and the U.S. and British embassies, the U.S. military said.

One mortar hit the Salhiya district, just outside the Green Zone, killing an Iraqi garbage collector and injuring another, according to a cameraman at the scene.

"This poor guy was just doing his job and he has been killed by a mortar ... intended for the coalition," local resident Muthana Joma Hassoun said.

A military spokesman, speaking on condition of anonymity, said mortar fire injured 14 soldiers, but their nationalities, the exact location of the attack and the seriousness of their wounds were not immediately clear.

South of Baghdad, gunmen assassinated the assistant director of Mahmoudiya Hospital, the hospital's chief said today.

Dr. Qassem el-Obaidi was shot dead by assailants in a car as he was driving home from work late Monday, said the hospital's director, Dr. Daoud al-Ta'i.

The violence has deeply hampered efforts to rebuild Iraq and made countries reluctant to send troops to assist the new government.

In the southern city of Basra, about 50 armed members of firebrand Shiite cleric Muqtada al-Sadr's personal militia snatched about 20 people Monday during raids against people selling and drinking alcohol, police said. The detainees were later handed over to police. During the raids, militiamen dragged men out of their houses and smashed cartons of canned drinks, apparently beer, Al-Arabiya TV showed in broadcast footage.

The Egyptian diplomat's kidnappers said they had seized him to deter his country from giving security aid to Iraq. An Egyptian official in Cairo said no ransom was paid, and the kidnappers released Qutb after realizing Egypt was not sending troops.