Efforts are continuing to secure the release of Egypt's ambassador to Iraq, who was seized in Baghdad on Saturday.
Mr Sherif had only been in Iraq for five weeks before he was kidnapped
No group has claimed responsibility for the abduction of Ihab al-Sherif, whose family has pleaded for his freedom.
US and Iraqi forces have arrested at least 100 suspected militants in raids in the capital, the US military said.
The operation targeted suspected insurgent hideouts west of the airport. It was not clear whether the raids were linked to Mr Sherif's kidnapping.
Those captured included foreigners, the US military said.
Elsewhere in the capital, two civilians have been killed in a car bomb that appeared to be an attempt to target an American military patrol.
Cairo has appealed to the kidnappers to treat Mr Sherif well and view him as an Arab patriot.
Foreign Minister Ahmed Aboul Gheit said officials at both countries' embassies in Iraq and Egypt were working to secure Mr Sherif's release.
Witnesses said Mr Sherif was snatched by gunmen while buying a newspaper from a Baghdad street.
Correspondents say the kidnappers may have been angered by Egypt's decision to designate Mr Sherif an ambassador, following his arrival in Iraq five weeks ago.
Monday's car bomb was reportedly detonated by remote control
The move made Egypt the first Arab country to upgrade ties with Iraq.
A prominent Sunni Muslim political organisation, the Iraqi Islamic Party, condemned the kidnapping and called for Mr Sherif's release, the Associated Press reports.
Iraqi Shia lawmaker Abbas al-Bayati described the kidnapping as "a message from the terrorists to the Arab countries not to open embassies in Iraq," the agency said.
In Cairo, the diplomat's elder daughter said her mother collapsed after she heard news of his capture.
"A state of panic looms over our house," Inji al-Sherif told Egypt's Al Ahram newspaper.
The US has been encouraging Arab countries to appoint ambassadors to Baghdad in an attempt to strengthen the new state and undermine the insurgency.
Many withdrew their ambassadors from Iraq after Saddam Hussein invaded Kuwait in 1990.
Last July, militants briefly kidnapped Egyptian diplomat Mohamed Mamdouh Qutb.