Walter Koenig, who played the spirited Russian crewman Pavel Chekov in the original Star Trek TV series, has died aged 90, his agent confirmed.

The US actor was a mainstay on the show from season two in 1967 until it ended in 1969, later reprising his role as the eager and earnest Chekov - with his Monkees-style mop-top haircut - in the six original cast movies from 1979 through to 1991.

He also wrote an episode for the show's animated spin-off.

In the mid-late 1990s, Koenig portrayed a very different character, the ruthless Psi Corps telepath Alfred Bester, in another sci-fi space series, Babylon 5.

Representatives for Koenig said in a statement given to the BBC: "Today we mourn the passing of Walter Koenig, whose talent, warmth, and unforgettable performances left a lasting mark on generations of fans around the world."

They confirmed he had died "of old age at home in North Hollywood" on Sunday night, "surrounded by his daughter and niece".

Koenig's Star Trek co-star and friend George Takei, who…