Counterterrorism officers detained one of the men in Birmingham and the other in Manchester, about 85 miles north of Birmingham. The pair "remain in custody for questioning," according to a statement from the Greater Manchester Police.
Assistant Chief Constable Dominic Scally of the Greater Manchester Police has said that counterterrorism officers are assisting their U.S. counterparts in the probe of Saturday's hourslong standoff between American authorities and a hostage-taker at the Congregation Beth Israel in Colleyville, Texas, about 27 miles northwest of Dallas.
An armed man claiming to have planted bombs in the synagogue interrupted Shabbat services on Saturday just before 11 a.m. local time, taking a rabbi and three other people hostage, according to Colleyville Police Chief Michael Miller.
One hostage was released uninjured at around 5 p.m. CT on Saturday, Miller told a press conference later that night. An elite hostage rescue team from the Federal Bureau of Investigation then breached the synagogue at about 9 p.m. CT, after hearing the hostage-taker say he had guns and bombs and was "not afraid to pull the strings," according to a joint intelligence bulletin issued Wednesday and obtained by ABC News.
"As a tactical team approached to make entry to the synagogue, the hostages escaped and were secured by tactical elements," the bulletin said. "The assault team quickly breached the facility at a separate point of entry, and the subject was killed."
No hostages were injured during the incident, according to Miller.
The slain suspect, identified by the FBI as 44-year-old British citizen Malik Faisal Akram, was from the Blackburn area of England's Lancashire county, about 20 miles northwest of Manchester, according to Scally.
A motive for the siege is under investigation. The FBI said in a statement Sunday that the incident "is a terrorism-related matter, in which the Jewish community was targeted, and is being investigated by the Joint Terrorism Task Force"
During the negotiations with authorities, Akram "spoke repeatedly about a convicted terrorist who is serving an 86-year prison sentence in the United States on terrorisms charges," according to the FBI.
Multiple law enforcement sources told ABC News that the hostage-taker was demanding the release of Aafia Siddiqui, who is incarcerated at Carswell Air Force Base near Fort Worth, about 16 miles southwest of Colleyville. Siddiqui, who has alleged ties to al-Qaida, was sentenced to 86 years in prison after being convicted of assault as well as attempted murder of an American soldier in 2010.
Two teenagers were arrested in southern Manchester on Sunday evening in connection with the synagogue attack. They were questioned and later released without being charged, Greater Manchester Police said in a statement Tuesday. Multiple law enforcement sources told ABC News that the teens are Akram's children.
Akram has ancestral ties to Jandeela, a village in Pakistan's Punjab province, the local police chief told ABC News. He visited Pakistan in 2020 and stayed for five months, the police chief said, a duration that may have been necessitated by COVID-19 restrictions.
Akram has been separated from his wife for two years and has five children, according to the police chief.
Law enforcement sources told ABC News that British authorities investigated Akram about a year ago and concluded he posed no threat that would have prohibited his travel from the United Kingdom to the U.S.
After arriving in the U.S. last month via a flight from London to New York City, Akram stayed at homeless shelters at various points and may have portrayed himself as experiencing homelessness in order to gain access to the Texas synagogue during Shabbat services, multiple law enforcement sources told ABC News.
U.S. President Joe Biden, who called the hostage-taking incident "an act of terror," told reporters Sunday that investigators suspect Akram purchased a gun on the street. While Akram is alleged to have claimed he had bombs, investigators have found no evidence that he was in possession of explosives, according to Biden.
ABC News' Luke Barr, Aaron Katersky, Habibullah Khan, Josh Margolin and Joseph Simonetti contributed to this report.