"We received sad news today ... Kalashnikov died at the age of 94 after a prolonged illness," Viktor Chulkov, press secretary of thePresident of Russia's Udmurt Republic, said.
Kalashnikov had been admitted to an intensive care unit in Izhevsk, capital of the Udmurt Republic, in serious but stable condition in mid-November. In June, Kalashnikov reportedly underwent a surgery in Moscow to have a pacemaker implanted.
The automatic rifle that Kalashnikov designed became one of the world's most familiar and widely used weapons. Its comparative simplicity made it cheap to manufacture, as well as reliable and easy to maintain.
Though honoured by the state, Kalashnikov made little money from his gun. He once said he would have been better off designing a lawn mower, BBC reported.
AK-47, now believed to be in use in more than 100 countries, has been listed among the "outstanding inventions" of the 20th century.
In 2002, during a visit to Germany, Kalashnikov said that he was proud of his invention, but also saddened to know that the AK-47 rifles were widely used by terrorists.
The inventor died just a few hours after Kalashnikov Concern, an enterprise named after him, announced that the company was going to modernise its well-known AK assault rifle and increase its export.