MOSCOW, April 8 (Reuters) - Russia's Federal Security Service (FSB) said on Tuesday it had killed Moscow's most wanted man, Islamist insurgency leader Doku Umarov, in a combat operation.
A website sympathetic to the insurgency in the North Caucasus said on March 18 that Umarov was dead but the Russian authorities had not previously confirmed the report.
Umarov's Caucasus Emirate organisation has played a leading role in the insurgency aimed at creating an Islamist state in Russia's North Caucasus and says it was behind attacks in Moscow in 2010 and 2011 that killed a total of 77 people.
"As a result of a combat operation, the activity of the head of the terrorist organisation Caucasus Emirate, Umarov, was neutralised," Alexander Bortnikov, the head of the FSB, told a meeting of Russia's National Anti-Terrorism Committee (NAK).
His comments were distributed in a video clip by the NAK, which he oversees, one day after President Vladimir Putin delivered a speech to the FSB in which he said there must be no let-up in the fight against the militants.
Bortnikov gave no details of the combat operation in which he said Umarov was killed.
The death of Umarov is a breakthrough for Putin in the fight against the Caucasus Emirate, which is listed as a terrorist group by the United States, although it already has a new leader who identified himself as Ali Abu Mukhammad in a video posted on You Tube.
Putin crushed a separatist rebellion in Chechnya when he first rose to power 14 years ago but the insurgency has since spread to neighbouring Dagestan.
Umarov united local militant groups in the North Caucasus under his command in 2007 and led the violent struggle to create a caliphate in the patchwork of mainly Muslim provinces sitting on Russia's southern border.
(Writing by Gabriela Baczynska)