The Obama administration released thousands of convicted criminals -- including murderers and those convicted of sexual assault -- while they were awaiting deportation proceedings, according to a new report.

The Center for Immigration Studies, a Washington-based advocacy group, released the statistics on Monday, in its latest bid to draw attention to what analysts with the organization say are lax enforcement practices by the Obama administration.

The numbers showed that in 2013, Immigration and Customs Enforcement released 36,007 "convicted criminal aliens" while they were waiting for the outcome of their deportation cases. They represented a total of 88,000 convictions.

A spokesman for ICE told Fox News the individuals in question had already served their criminal sentences.

The majority of the cases involved individuals convicted on lower-level or nonviolent offenses, like auto theft, drunk-driving and drug charges. But many were involved in more serious cases.

According to the report, the 88,000 convictions included:

-- 193 homicide convictions

-- 426 sexual assault convictions

-- 303 kidnapping convictions

-- More than 1,000 aggravated assault convictions

Jessica Vaughan, the group's director of policy studies, said in a statement she was "astonished" by the figures. Referring to an ongoing Department of Homeland Security review of deportation policies, she said any "further relaxation of enforcement" would be "hard to justify" in light of the statistics.

"Congress should resist further action on immigration reform until the public can be assured that enforcement is more robust and that ICE can better deal with its criminal alien caseload without setting them free in our communities," she added.

ICE defended its enforcement practices when asked about the report, and said in a statement that many of those cited were released "under restrictions such as GPS monitoring, telephone monitoring, supervision, or surety bond."

Further, the statement said the agency was required by law to release some of those individuals.

"The releases required by court decisions account for a disproportionate number of the serious crimes listed in the report. For example, mandatory releases account for over 75% of the homicides listed," ICE said.

The individuals in question were reportedly released on bond or on parole or under various other alternatives to detention while awaiting processing.

The same organization that published the data put out a separate report more than a month ago that showed ICE agents were opting not to deport thousands of "criminal aliens." These are separate from the cases detailed in the latest study.

According to that prior report, ICE released 68,000 foreign nationals in 2013 who either had criminal convictions or charges against them.

Immigration and Customs Enforcement, though, accused CIS of distorting the numbers, and claimed that some of them could represent minor offenses. Further, the agency said a total of 216,000 "convicted criminals" were removed in 2013.