A lawyer says Palestinian hunger strike leader Marwan Barghouti denies the authenticity of a video purportedly showing him eating secretly in his cell.

Khader Shkirat, who met with Barghouti for three hours Sunday, says his client lost 13 kilograms (28 pounds) since a hunger strike by hundreds of Palestinians detained by Israel began April 17.

Shkirat says Barghouti told him he would escalate the protest soon by refusing to drink water. The prisoners seek better conditions.

Israel moved Barghouti into isolation at the start of the strike.

Last week, Israel released a video allegedly showing Barghouti snacking.

Shkirat says his client told him the cell featured in the video, with a bunk bed, is much nicer than the run-down single-bed cell with a smelly blanket where he is held.