WASHINGTON: The Obama administration is offering rewards of up to $20 million for information leading to the whereabouts of four top leaders of the Islamic State group.

Through its Rewards for Justice program, the State Department announced Tuesday that it would pay up to $7 million for information on Abd Al-Rahman Mustafa Al-Qaduli, up to $5 million each for Abu Mohammed Al-Adnani and Tarkhan Tayumurazovich Batirashvili and up to $3 million for Tariq Bin-Al-Tahar Bin Al Falih Al-’Awni Al-Harzi.

According to the department, Qaduli is a senior IS official who originally joined Al-Qaeda’s affiliate in Iraq, Adnani is an official IS spokesman, Batirashvili is a battlefield commander in northern Syria and Harzi is the group’s leader for the border region between Syria and Turkey.

Meanwhile, counterterrorism experts said IS has a history of asserting involvement in attacks in which it had no operational role. It followed IS’ claim of responsibility Tuesday for the assault on a Texas anti-Islam contest.

That suggests the two gunmen could have carried out their own lone wolf-style strike before they were shot and killed at the scene of Sunday's shooting in the Dallas suburb of Garland.

Federal officials identified the pair as Elton Simpson and Nadir Soofi, both Americans who lived in Phoenix. Federal authorities had been scrutinizing Simpson's social media presence recently but had no indication he was plotting an attack, said one federal official familiar with the investigation.

Rep. Michael McCaul, chairman of the House Homeland Security Committee, said a Twitter account linked to Simpson included images of Anwar Al-Awlaki, a radical cleric killed in a CIA drone strike in Yemen. Al-Awlaki was an American citizen.

Among the hashtags used by the account was “#texasattack.” And one of the final tweets was: “May Allah accept us as mujahideen,” or holy warriors.

“Was he on the radar? Sure he was,” McCaul said from Turkey, where he was leading a congressional delegation.

The evidence does not indicate the attack was directed by IS, “but rather inspired by them,” said McCaul, who was briefed on the investigation by federal law enforcement officials. “This is the textbook case of what we're most concerned about.”