The American government announced rewards totaling $20 million for information on four Islamic State leaders.
The US Department of State's Rewards for Justice Program named the four as
Abd al Rahman Mustafa al Qaduli
Abu Mohammed al Adnani
Tarkhan Tayumurazovich Batirashvili
Tariq Bin al Tahar Bin al Falih al Awni al Harzi.
It described them as "key leaders" of ISIS, which has taken control of large areas of Iraq and Syria. The group has also beheaded a number of foreign hostages.
There is a reward of up to $7m for information on al Qaduli, who rejoined IS in Syria after being released from prison in 2012.
He originally joined al Qaeda in 2004 and served as deputy to its leader Abu Musab al Zarqawi, who was killed in an airstrike in Iraq in 2006.
The US is also offering to pay up to $5m each for al Adnani and Batirashvili.
Al Adnani, who was born Taha Sobhi Falaha, is the official spokesman for ISIS and has "repeatedly called for attacks against Westerners and has vowed 'defeat' for the United States".
Georgian national Batirashvili is a senior ISIS commander and ran a prison where foreign hostages are thought to have been held in al Tabqa, in Syria's Raqqah province.
There is also a reward of up to $3m for al Harzi, who has helped raise funds for IS in the Gulf, and is the group's leader in the border region between Syria and Turkey.
The US government's highest terror reward is $25m for al Qaeda leader Ayman al Zawahiri.