The jihadist Islamic State group (IS) on Wednesday said it has beheaded Croatian hostage Tomislav Salopek, 31, abducted on July 22 in Egypt while working for a French firm.

Croatian Prime Minister Zoran Milanovic said he was unable to confirm Salopek's death.

"I don't know if we will be able to confirm that in the coming days, but what we see does not look good, looks horrible," he said.

Below is a list of previous executions of foreigners by militants or movements linked to IS.

-- 2014 --

- August 19: IS posts a video of the decapitation of US freelance photojournalist James Foley, 40, who was seized in northern Syria in November 2012.

The video of Foley's killing, which provokes worldwide revulsion, also shows a second US reporter, Steven Sotloff, being paraded by a black-clad IS militant who warns that he too will be killed unless President Barack Obama halts air strikes on IS in Iraq.

- September 2: IS says in another propaganda video it has beheaded Sotloff, 31. The freelance reporter was kidnapped August 2013 in Aleppo near Syria's border with Turkey. His abduction was kept secret under a news blackout.

- September 13: IS claims to have beheaded British aid worker David Haines, 44, as the US begins a diplomatic offensive to build an international coalition against the jihadists. Haines was seized in March 2013 while working for a Paris-based non-governmental organisation.

- September 24: IS-linked Jund al-Khilifa, or "Soldiers of the Caliphate", claims to have beheaded French tourist Herve Gourdel, 55, in Algeria, in a video posted online after Paris rejected their demand to halt air strikes in Iraq.

- October 3: IS claims in a graphic video to have beheaded British aid volunteer Alan Henning, 47, in Syria in response to British air strikes in Iraq. He was abducted in December 2013 while helping deliver aid to a Syrian refugee camp.

- November 16: IS says it executed Peter Kassig, a 26-year-old US aid worker kidnapped in Syria in October 2013, as a warning to Washington.

The same video showed the simultaneous beheadings of around 15 men described as Syrian military personnel, in the latest IS mass execution.

-- 2015 --

- January 8: Libya's IS branch claims to have executed two Tunisian journalists missing since September, Sofiene Chourabi and Nadhir Ktari.

The two were captured by an armed group near the town of Brega on September 3, but were released a few days later before being detained by a militia and then disappearing.

- January 24 and 31: IS claims to have beheaded Japanese self-declared "security contractor" Haruna Yukawa, 42, and a week later respected war correspondent Kenji Goto, 47, who had been searching for him in Syria.

- February 3: The group releases a video showing 26-year-old Jordanian fighter pilot First Lieutenant Maaz al-Kassasbeh, who was captured in December after his plane crashed, being burned alive inside a metal cage.

According to a Syrian NGO, the jihadists have executed more than 3,000 people, including 1,800 civilians, in Iraq and Syria where they declared an Islamic caliphate in June 2014 in territory they control.

In February, jihadists in Libya linked to IS claimed the execution of 21 Coptic Christians, all but one of them Egyptians, and in April the execution of 28 Christians, all Ethiopians.