A Yemeni immigrant and longtime U.S. citizen sued the State Department in a San Francisco federal court Monday, accusing the U.S. Embassy in the war-torn nation of barring him from leaving the country for more than a year with false accusations of passport fraud based on a coerced confession.

The same thing has reportedly happened to several dozen Yemeni Americans who were stripped of their passports at the embassy in Sanaa based on concocted claims that they obtained the travel documents under false names, said attorneys from the Asian Law Caucus who filed the suit on behalf of Mosed Omar.

“Many people are stuck in Yemen in a war zone not because they ignored travel warnings, but because the embassy turned its back on them,” said attorney Yaman Salahi.

Still without a passport, “I cannot travel to see my daughter” in Yemen, Omar said outside the federal courthouse. “I want to help her get out of the war.”

Omar, 64, is seeking the return of his passport and a court order requiring the State Department to follow uniform procedures in such cases, revoking a passport only if there is “clear and convincing evidence” that it was obtained by fraud.

The State Department did not immediately respond to a request for comment.

According to his lawsuit, Omar moved to the United States from Yemen in 1972 and became a citizen in 1978 as an American’s adopted son. He worked in an auto factory in Detroit for 10 years, then moved to California and owned small grocery stores for 20 years. He lives in San Francisco with some of his children and grandchildren, and suffers from diabetes and high blood pressure.

With conditions in the Middle Eastern nation worsening, and the State Department advising Americans to leave, Omar went to Yemen in July 2012 to bring back his youngest daughter, who was 13. He heard nothing until January 2013, when an official told him there was good news about his daughter’s passport and told him to come to the embassy, the suit said.

When he arrived, his passport was taken away and he was subjected to two interrogations in the next few hours, with limited help from an interpreter, the suit said. It said he was given no food, water or medication, had no way to contact his family, and after nine hours was feeling so weak and desperate that he offered to do anything necessary to retrieve his passport and go home.

Soon after, Omar said, he was brought into the interrogation room and told to sign papers that he couldn’t understand, because of his limited English, or even read, because of blurred vision. They contained an admission that he had obtained his passport under a false name, the suit said.

The embassy kept his passport, and Omar, his health deteriorating, remained in Yemen until February 2014, when he was provided a one-way travel document and returned home without his daughter.

At an appeal hearing in Washington, D.C., in September, Omar attested to his real name with numerous U.S. documents, and statements from four Yemenis who had known him before he emigrated, but the State Department upheld the embassy’s findings, the lawsuit said. The suit cited reports last year by Al Jazeera America and the Guardian newspaper of other Yemeni Americans whose passports were confiscated after similar interrogations at the same embassy.

An older daughter, Naeema Omar, said her father had suffered a heart attack a few weeks after his return in 2014.

“Imagine building your family for 40 years,” she said, “and then having some embassy officer take it away from you.”

Bob Egelko is a San Francisco Chronicle staff writer. E-mail: begelko@sfchronicle.com Twitter: @egelko