WASHINGTON—Members of a congressional committee Wednesday accused the FBI of stymieing their inquiry into the Boston Marathon bombings after the bureau’s refusal to reveal what it knew about the older suspect, Tamerlan Tsarnaev, prior to the attacks.

The frustrations, aired publicly after FBI officials rebuffed an invitation to appear before the House Homeland Security Committee, stemmed from the FBI’s unwillingness to detail how it handled its earlier review of Tsarnaev, who was killed in a firefight with police in Watertown after being identified as a suspect in the April 15 bombings.

“I went to Russia and was given more information,” said committee member Representative William Keating, a Democrat from Bourne who has been seeking information about Russian warnings to American authorities about Tsarnaev’s increasing radicalism dating to 2011.

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The Committee chairman, Republican Michael McCaul of Texas, opened the hearing on the bombings yesterday with a broadside aimed at the FBI.

The agency “continues to refuse this committee’s appropriate requests for information and documents crucial to our investigation into what happened in Boston,” McCaul declared. “The information requested by this committee belongs to the American people. It does not belong solely to the FBI, and I sincerely hope they do not intend to stonewall our inquiry into how this happened.”

The FBI interviewed the elder Tsarnaev in his Cambridge home in the spring and summer of 2011 but concluded at the time he was not a threat and closed its inquiry. The bureau apparently did not reopen the case, despite additional warnings from Russia later that year, the subsequent decision by the CIA to add him to a database of potential terrorist suspects, and a tip in 2012 from the Department of Homeland Security that he traveled to Russia.

The FBI Wednesday strongly refuted accusations that it was being uncooperative with Congress. It has said in the past that local authorities in Boston had access, in the years before the bombings, to the same information about Tsarnaev on its computers as FBI agents.

“We are not stonewalling. We have briefed [the] committee on several occasions and will continue to do so as necessary,” said Paul Bresson.

He said the FBI did not provide a witness for the Wednesday hearing in order to avoid compromising the legal case against the surviving Tsarnaev brother, Dzhokhar, who pled not guilty Wednesday to 30 charges in his first appearance in court in Boston.

“We have an obligation to protect the integrity of the judicial process while it is ongoing,” Bresson said. “This involves ensuring both the government’s ability to conduct a successful prosecution as well as the rights of all parties involved including the victims and the defendant who, as it turns out, has a court appearance on the same day as this hearing.”

During another hearing on the bombings across the Capitol in the Senate, meanwhile, Boston Police Commissioner Edward F. Davis renewed his calls for the FBI to reveal more information about potential terror threats to local police departments.

“If we do that we’re a much stronger as a nation,” he testified. “If we don’t, it puts our communities and my officers at risk.”

Davis also said the city needs more and better cameras on the streets, which is likely to spark renewed debate over privacy. He said the city has traffic cameras downtown and on major roadways. But there were no cameras along the parade route, and the existing cameras were not set up to record prior to the bombing, he said.

House Homeland Security Committee members were frustrated by a July 3 letter to the committee from the FBI. Reviewed by the Globe, the letter said the bureau would not be responding to all the committee’s requests for information. A key piece of information the committee wants is the original Russian warning to the United States in 2011, which said Tsarnaev might be planning to travel to Chechnya to meet with Islamic radicals.

“We don’t even have that copy [of the Russian warning] in this committee,” Keating said in an interview after the hearing.

The FBI has insisted that the Russian warning was vague and that several of its requests to the Russians for more information went unanswered. But Keating said the Russians told him, during his own fact-finding trip to Russia in late May, that they don’t know what requests for information the FBI had referred to.

``Where’s the request? Tell us the name, tell us the time, to whom that they have sent it to,” Keating demanded. “What I want ultimately is a timeline—a very distinct timeline—of everything that happened.”

Keating, a former Massachusetts prosecutor, also said that he believes the FBI is using the ongoing case of Dzhokhar Tsarnaev as an excuse to not be more forthcoming. He said he does not believe the FBI’s contention that revealing information about its earlier review of Tamerlan Tsarnaev would jeopardize the case.

And he said he is not persuaded by the FBI’s previous responses that it investigated Tsarnaev in 2011 and closed its case after an initial inquiry.

“The answer we keep getting back is that it wouldn’t have mattered any way because the case was closed,” keating said. “Case closed stopped everything and, in fact, became an excuse for why other things weren’t done.”

Other panel members, Democrats and Republicans, were critical of the FBI’s level of cooperation.

“The fact that the FBI is not sharing information with this committee with jurisdiction over homeland security I think is just totally unacceptable,” said Representative Peter King, a Republican of New York. “I think the FBI has a lot to explain for here.”

McCaul, the committee chairman, pledged to keep up the pressure on the FBI to cooperate.

“I said when I started this investigation that we were going to find out what happened, what went wrong and how to fix it,” McCaul said, “and I will not be satisfied until we get the answers that the American people deserve.”