A militant group in Gaza released a video on Wednesday showing Sasha Troufanov, an Israeli Russian dual citizen who has been held hostage since the Hamas-led attack on Israel 13 months ago.

It was the first video of Mr. Troufanov since Palestinian Islamic Jihad, the second most powerful militant group in Gaza after Hamas, released two videos of him in May. It was not clear when the video was filmed, but in it he refers to having been held in Gaza for a year. He also says he is 28, an indication that it was shot before Nov. 11, his 29th birthday.

The release of the video brought some renewed attention to the plight of the dozens of hostages still believed to be alive in Gaza, who have endured more than a year of war in captivity. In it, Mr. Troufanov appears weary, with an untrimmed beard and bags under his eyes. He speaks of a lack of food and water.

His mother, Lena Troufanov, responded to the video with alarm.

“I am relieved to see my son alive, but I am very worried to hear what he is saying,” she said in a statement shared by an Israeli hostage families support group. “I urge that every effort be made to secure his immediate release and that of all other hostages. They have no time left.”

Rights groups and international law experts say that a hostage video is, by definition, made under duress, and that the statements in it are usually coerced. Israeli officials have called the videos of hostages periodically released by Hamas and Islamic Jihad during the war as a form of “psychological warfare,” and experts say their production can constitute a war crime.

Last month, Mousa Abu Marzouk, a senior Hamas official, told Russia Today that Hamas would give “priority” to Mr. Troufanov’s release in any exchange of hostages and Palestinian prisoners, “in honor” of President Vladimir Putin of Russia. He said Hamas had spoken to Islamic Jihad about Mr. Troufanov.