British photographer John Cantlie has appeared in a new video released by the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group.

The video, which was posted on social media late on Saturday, purported to show Cantlie in the Iraqi city of Mosul, which was captured by the group in the summer of 2014.

Cantlie was one of about a dozen Western hostages held by the group over the past four years. Several were killed, and others released after ransoms were paid.

The journalist has fronted a series of ISIL propaganda films but had not appeared in any for more than a year, raising fears that he had been killed. His supporters have rubbished the videos, saying that he is speaking under duress.

In the latest clip, which was not dated, Cantlie talks about what he says are ineffective US-led coalition air strikes on ISIL targets in the city.

The release of the video came less than two weeks after a US strike killed the group's military commander, Omar al-Shishani.

The Georgian national, born Tarkhan Batirashvili, is one of the highest-ranking ISIL leaders killed by US forces since they started an air campaign against the group in 2014.

Hostage killings

Cantlie, who appeared significantly thinner than in previous videos, is believed to be the last Western hostage held by ISIL in Iraq or Syria.

The group killed journalists James Foley and Steven Sotloff, and aid worker Peter Kassig, who were all US citizens. British aid workers Alan Henning and David Haines were also killed.

The masked man responsible for those killings, British national Mohammed Emwazi, was killed in a US strike on the Syrian city of Raqqa in January.

ISIL continues to hold Mosul, Raqqa and a large swath of territory in Syria and Iraq. The group is at war with the Syrian government and opposition groups, Kurdish factions, Iranian-backed militias, the US-backed coalition, and other armed factions.

Cantlie was previously captured by an armed group in Syria but escaped, only to be captured again after another visit to the country.