A previously unknown verse attributed to Federico García Lorca has been discovered 93 years after the celebrated Spanish poet and playwright is believed to have jotted it on the back of one of his manuscripts.

Lorca is thought to have written the eight-line poem in 1933 while working on the collection Diván del Tamarit, a homage to the Arab poets of his native Granada.

The newly discovered verse was found on the reverse of a manuscript of one of the Tamarit poems – Gacela de la raíz amarga – which the flamenco singer and Lorca enthusiast Miguel Poveda bought from a German antiquarian.

It has since been verified by the Lorca expert Pepa Merlo and will feature in a forthcoming book.

The brief verse, composed three years before Lorca was murdered in the early days of the Spanish civil war, reveals the poet’s familiar preoccupation with the passing of time: “The clock sings / I count the hours mechanically / Seven o’clock; twelve o’clock / It’s all the same / I am not here / It is the mark of flesh / That I left behind when I departed / So as to know my place / Upon my return.”

Poveda, who recently led efforts to turn Lorca’s childhood home into a cultural centre dedicated to the poet’s life and work, said he had been deeply moved by the fortuitous discovery.

“My attention was grabbed when Pepa Merlo said to me, ‘That’s Federico’s handwriting. You’ve got something new by Federico there’,” he told the state broadcaster TVE on Thursday.

“For me, it’s a heartfelt gift. It’s all there in those lines, ‘It is the mark of flesh / That I left behind, when I departed / So as to know my place / Upon my return’.”

Merlo said that while the verse may have been overlooked because it was scribbled on the back of another work, it nonetheless revealed “the importance that the concept of time held for Lorca”.

The gay, progressive writer – whose works include Gypsy Ballads, Poet in New York, Blood Wedding, Yerma, and the House of Bernarda Alba – was shot by a rightwing death squad in August 1936, becoming perhaps the most prominent victim of Spain’s three-year civil war. His body has never been found and is thought to lie in a shallow grave at the bottom of a mountain slope near Granada.

Interest in Lorca has only grown as the centenary of his death draws near. Last summer, a facsimile edition of the poet’s homoerotic, anguished – and posthumously published – Sonnets of Dark Love was issued to bring the poems to a new readership.

Although long known to Lorca scholars, the sonnets had been hidden away by the poet’s family, who believed their tortured and sensual lines would taint his legacy and stir up old hatreds.

The newly discovered poem will be published in a book written by Poveda and Merlo titled Las cosas del otro lado. lo inédito en Federico García Lorca (Things from the Other Side: the Unpublished in Federico García Lorca).