UPDATE 2/24 7:58 AM: Here is an English translation of the below video message:
Emir Abu Usman (aka Dokku Umarov):
I seek refuge in Allah from the accursed Satan, in the name of Allah the Most Compassionate, the Most Merciful.
Praise be to Allah the Creator of the Worlds and peace and blessings be on upon His prophet (pbuh) and his family and companions and those who follow him on the true path.
Peace and blessings be upon all the holy warriors who are following the footsteps of our Prophet (pbuh) today.
Today, I am visiting a base of the Martyr Brigade Riyad-us-Saliheen, with our brother Khamzat, the Emir of this brigade, praise be to Allah Who allowed in His mercy for us to meet.
I want to say some words which will give you an idea why these special operations are carried out and why we are compelled to carry out such operations.
The blame for the suffering of these people does not fall on us but on Putin, the enemy of God. We all can see this lawlessness that is being committed today, in the Caucasus in the first place.
We also observe that this same lawlessness is now being committed in Russia. This lawlessness is staged on purpose because Russia is cheating, hampering and deceiving its people in Russia’s obligations before it. That is why they carry out such provocations in order to direct the people’s anger at something else.
We observe that the infidels, Russia, occupied the Caucasus and made it its testing ground and an experimental base. They make experiments on the lives of Muslims, kill them, bury them alive, they do what they want with them, everything what they need for their experiments and their scientific works. But that is too little for them, they set their dogs on those Muslims, on those Caucasian brothers who are now forced to live on the territory of Russia, in Moscow, Leningrad and other cities. These dogs attack the Caucasians in large numbers. Therefore, the Caucasians are forced to defend themselves. That is how they create propaganda and try to set on the Caucasians the anger of their human cattle.
Therefore we are forced to respond to this lawlessness, although what we do is not lawlessness, because, God willing, that is called a special operation. We sacrifice our life while carrying out the special operation.
Today, I am weeping. Why? Because, we, the Emirs, are forced to send out the best of the best from among us on special operations. So I am simply weeping because our brother leaves this world before me. But praise be to God, I am happy for him inside me because this world is worth of leaving it.
So we are forced to act, to carry out these special operations. This special operation will be carried out exactly against those people who attack the Caucasians and mock at the Caucasians, and try to manifest their hatred to our Muslim brothers being instigated by Putin and his pack of dogs.
You are to manifest this hatred first of all to your authorities and demand from them that they leave the Caucasus . And we will never visit Russia, and will never see your faces because we manage without doing that.
If you swallow in silence this fraud that Putin and his dogs offer you, we are forced to try to awaken you with our actions.
If this is not enough, then God willing, more strikes will follow. I can say with absolute confidence that if it is the Almighty’s will and if God’s mercy is upon us, then we will make this year a year of blood and tears for you. That is why I ask those citizen whose heads are not filled with garbage to awake and to understand what we are striving for, so that they understand who exactly is responsible for this massacre, for blood, for tears that we are now forced to sacrify . We now establish the word of God, God willing, and our blood, and our tears, all that is justified and paid for. And your blood, and your tears, all that throws you in fire, believe me.
In conclusion, I would like to say again that I will not tell you that we have hundreds prepared for martyrdom, but that 50 to 60 of them will be found, God willing. Depending on your reaction, depending on your actions, these operations, God willing, will be carried out monthly, weekly, as often as God allows us. May God reward you with Greatness and my last supplication is to praise God, the Lord of the worlds. The Emir of Riyad-us-Saliheen, Khamzat, will also add a few words for you.
I seek refuge in Allah from the accursed Satan, in the name of Allah the Most Compassionate, the Most Merciful, peace and blessings be upon the Messenger (pbuh) of Allah.
I have nothing to add except to ask God to accept my prayer for our brother that we are sending out.
We do not send him out because he is superfluous. But since the Russian commanders here, Putin and other like him who establish order in the Caucasus, are lawless, and they do everything they wish and you sit silently in Russia, we do that not just in order to kill somebody or to spill some blood – we simply want that you to understand that it won’t do that we bleed and you drink milk.
You’d better come to senses and start thinking and ask your higher-ups, who hide behind your backs and call us various names – terrorists, Islamists and name their actions in the Caucasus as “anti-terrorist operations.”
You have to think about that and not lash out at us, at our Caucasian people, but you should ask your high commanders.
We send out our brother with bitterness because he is leaving us, God willing, we will pray for him that his expedition is for the good of Islam and that the word of God is supreme.
Praise be to God! May peace be with you and the mercy and blessing of God be upon you.
Emir Abu Usman:
And now we give word to our brother. First of all, I wish with trembling in my soul, and I pray the Almighty to accept our brother in the circle of the Prophet (pbuh) and that he waits for us in paradise and, God willing, God will judge according to intentions. And the intentions of our brother are sincere. So our brother Seyfullah says a few words.
Praise be to Allah, the Lord of the worlds! Peace and blessings be on Muhammad, peace be with you and the mercy and blessing of Allah be upon you.
I am a mujahid in the sabotage brigade of Riyad-us-Saliheen under the command of Emir Khamzat and under the command of the supreme Emir Abu Usman. I am preparing for a special operation to carry it out for the sake of God in order to make the word of God supreme on this Earth, and not only in the Caucasus but in the whole world. And so that the infidel, Putin or Medvedev, it makes no difference, so that the infidel, the enemy knows that there are many of us, that after me come other brothers who are ready to sacrifice their lives for the sake of God, to spill their blood to make the word of God supreme. We went out for war for the sake of God, to free our lands from the enemy, from the infidel. And this is my last word.
Praise be to Allah, the Lord of the worlds. Peace be with you and the mercy and blessing of God be upon you.
NOTE: Below is an implicit claim of responsibility from Dokku Umarov for the Domodedovo attacks, which occurred last month. According to the Kavkaz-Jihād Blog, Umarov visited the base of the Riyāḍ us-Ṣāliḥīn Martyrs Brigade and released this video with its amīr named Khamzat and another individual named Sayfullah. Umarov stated he arrived at their base prior to sending Sayfullah on a special task in Russia, most likely referring to the Domodedovo attacks. Here are some key quotes from the below video:
“God willing we will make this year a year  of blood and tears for you [Russia]”
Attacks were a response to “lawlessness” unleashed on the region by Prime Minister Vladimir Putin and “his pack of dogs.”
“You better come to your senses and think”
Bombings would go on as long the “crimes committed by the gangs under Putin continued”