U.S. diplomats in Libya repeatedly asked the Obama administration for more security in Benghazi in the run-up to the Sept. 11 attack on the consulate but were "denied these resources," two congressional lawmakers said.

House oversight committee Chairman Darrell Issa, R-Calif., and Rep. Jason Chaffetz, R-Utah, pressed Secretary of State Hillary Clinton for more information on those requests and other concerns in a letter Tuesday.

They detailed a string of attacks and other security incidents in Benghazi starting in April, and asked the State Department what measures it took to address the threat. They claimed officials have told the House Oversight and Government Reform Committee of "repeated requests" for additional security.

"Based on information provided to the committee by individuals with direct knowledge of events in Libya, the attack that claimed the ambassador's life was the latest in a long line of attacks on Western diplomats and officials in Libya in the months leading up to September 11, 2012," they wrote. "In addition, multiple U.S. federal government officials have confirmed to the committee that, prior to the September 11 attack, the U.S. mission in Libya made repeated requests for increased security in Benghazi. The mission in Libya, however, was denied these resources by officials in Washington."

A State Department spokeswoman said Tuesday that Clinton plans to respond to the lawmakers' questions.

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The House committee plans to hold an Oct. 10 hearing on security in the region leading up to the attack. The letter to Clinton alleges 13 incidents that showed the deteriorating security situation on the ground.

The reported incidents include an account that members of the Libyan security force were urged by their family members to quit over rumors "of an impending attack."

The letter also said threats on Facebook prompted Ambassador Chris Stevens to stop taking morning runs around Tripoli, though he reportedly later resumed those runs. The letter included other incidents, which have been well documented, including the June attack on a convoy carrying the British ambassador. Plus it said "assailants" put an explosive device at the gate of the U.S. Consulate in early June, blowing a hole in the security perimeter.

"Put together, these events indicated a clear pattern of security threats that could only be reasonably interpreted to justify increased security for U.S. personnel and facilities in Benghazi," the lawmakers wrote.

Stevens and three other Americans were killed in the attack on the U.S. Consulate in Benghazi on Sept. 11.

Fox News reported on Friday that the physical security was so substandard at the Benghazi consulate that it required a waiver, signed off in Washington by the secretary of state, the head of diplomatic security, or the heads of foreign building operations. A State Department spokeswoman said there would be no comment on the issue until their internal investigation is complete.

The department, meanwhile, has stood by U.S. Ambassador to the U.N. Susan Rice in the face of criticism and calls for her resignation. Rice came under fire for claiming repeatedly the Sunday after the attack that it was a "spontaneous" reaction to protests over an anti-Islam film. The administration now acknowledges the assault was a coordinated terror attack.

Fox News' Catherine Herridge contributed to this report.