The Iraqi government says 887 people have been arrested during a two-week crackdown on the insurgency in Baghdad.
Thousands of Iraqi and US soldiers took part in Operation Lightning
Operation Lightning has not dealt a "knockout blow" to the insurgency, but signals its "slow death", government spokesman Leith Kubba said.
He said the operation had expanded both to the "triangle of death" south of the capital and to cities in northern Iraq.
But a prominent Sunni Muslim group accused the government of targeting Sunnis and opponents of the occupation.
The Iraqi government says 608 mobile and 194 permanent checkpoints have been established around Baghdad since Operation Lightning began on 22 May, according to the Associated Press news agency.
Before the operation, authorities controlled only eight of the 23 entrances to Baghdad, but now they control them all, AP says.
"Despite a tangible improvement in the situation in Baghdad, we must not have a false sense of security," Mr Kubba is quoted as saying by the AFP news agency.
"All indications show that there is a retreat by these networks, but they are still doing one or two operations to prove that they are alive.
"The success in Baghdad is now being repeated in Mosul with the help of local residents and tribes."
Some 40,000 US and Iraqi troops are said to be involved in Operation Lightning, but Baghdad residents say they have seen little sign of them in the capital.
But Sheikh Abdel Salam al-Kubaisi, of the Association of Muslim Scholars, accused security forces of being "out to get Sunni Arabs... and all those who oppose the occupation".
He said the government was fuelling sectarian tensions and that the association would hold the government responsible for the fate of those arrested - the majority of whom were not terrorists, he said.
Mr Kubba also backed away from earlier suggestions that Saddam Hussein would be brought to trial within two months.
On Monday, the Iraqi Special Tribunal established to try members of the former regime denied there was any schedule to try the former leader, and in a statement reiterated its independence from the government.
"A fixed date has not been presented," Mr Kubba said.
"[The Special Tribunal] assured me that they have a media official and they wish that information is given by them directly. I refer you to the spokesman for the tribunal."
A tribunal spokesman was also reported to have rejected government statements that Saddam Hussein would only be charged with 12 of the crimes of which he is accused to speed up the process of bringing him to trial.