Princeton University graduate student Elizabeth Tsurkov held captive in Iraq by Iran-linked Shiite militia

LONDON -- A Princeton University graduate student is being held captive by an Iran-linked Shiite militia in Iraq where she was conducting field research for her Ph.D. in political science, according to officials and colleagues.

The Israeli Prime Minister's Office announced in a statement on Wednesday that Elizabeth Tsurkov, an Israeli-Russian dual citizen, "has been missing in Iraq for several months and is being held by the Shiite militia Kataib Hezbollah."

Kataib Hezbollah is designated by the United States as a terrorist organization, accused of targeting American forces in Iraq. It is one of the most hard-line and powerful militias in Iraq, with close ties to Iran's elite Islamic Revolutionary Guards Corps. Kataib Hezbollah is separate from the Iran-backed militant group Hezbollah in Lebanon.

"Elizabeth Tsurkov is still alive and we hold Iraq responsible for her safety and well-being," the Israeli Prime Minister's Office said. "She is an academic who visited Iraq on her Russian passport, at her own initiative pursuant to work on her doctorate and academic research on behalf of Princeton University in the U.S."

There was no immediate comment from Iraqi officials.

Tsurkov would not have been allowed to enter Iraq on her Israeli passport, since the two countries do not have diplomatic relations and Iraq considers Israel a hostile state.

Princeton University, located in Princeton, New Jersey, released a brief statement on Wednesday saying Tsurkov is "a valued member" of the school's community.

"We are deeply concerned for her safety and well-being, and we are eager for her to be able to rejoin her family and resume her studies," the university added, without providing more details.

The New Lines Institute for Strategy and Policy, a think tank in Washington, D.C. where Tsurkov is a non-resident fellow, published an article via its New Lines Magazine on Wednesday saying Tsurkov had informed her colleagues on March 19 that she was done with fieldwork and wanted to return to Princeton University to write her doctoral dissertation.

"We were relieved. We did not want her to stay in an Iraq that was increasingly dominated by pro-Iranian militias," the New Lines Magazine wrote. "Just over a week later we learned from our sources that a pro-Iranian militia had kidnapped her in Baghdad, where she had been doing research. We have not heard from her since."

Tsurkov's family had requested that her abduction not be publicized in hopes of negotiating a quick release, according to the magazine.

"What followed Liz's kidnapping were months of public silence but nonstop efforts to learn more about her situation," the magazine added.

The magazine noted that Tsurkov's fieldwork "poses no threat to anyone," however, as an Israeli national, "there are parts of the Middle East where her very identity places her at grave risk."

"But Liz is committed to a specific style of granular, hyperlocal research that requires fieldwork, and she never seems frightened of anything," the magazine wrote. "She stayed in Iraq."

Tsurkov is also "an outspoken critic of all three of the major likely players involved in negotiating her release: Israel, Iran and Russia," which complicates matters, according to the magazine.

"All of us feel that the United States needs to be involved in some way in helping Liz," the magazine wrote. "She is not a U.S. national, and her disappearance did not trigger the sort of aggressive U.S. reaction that an American's might. But Liz is very much a part of America. She works with a Washington think tank, writes for an American magazine and studies at Princeton University. She deserves America's every effort to bring her to safety."

ABC News has reached out to the U.S. Department of State for comment.

ABC News' Laryssa Demkiw and Conor Finnegan contributed to this report.