A Lebanese man believes he has grown the world's heaviest potato – a monster weighing 24.9lb – at his farm in the south of the Mediterranean country.

The weight of the knobbly root vegetable has not yet been verified by the Guinness Book of Records, but could be several times heavier than the existing record holder – a 7lb 13oz spud grown in the Isle of Man.

"I've been working the land since I was a boy, and it's the first time I've seen anything like it," said Khalil Semhat, 56, a farmer near the city of Tyre 50 miles south of Beirut.

Describing his find as a "giant", Mr Semhat displayed the potato for a photographer on a large set of scales.

The tuber was so heavy Mr Semhat said he had to call on a friend to help him pry it from the ground, according to AFP.

His farm, damaged during Israel's heavy bombardment of south Lebanon during a brief war in summer 2006, mostly grows potatoes and bananas.

Despite the freakish size of the vegetable, Mr Semhat insisted he had used no artificial fertilisers: "I didn't use any chemicals at all," he said.

Mr Semhat hopes to have the potato registered by Guinness in its next book of records.