Turkey reportedly banned some social media sites after the Isis video emerged online.
The reward for information leading to the arrest of the Isis figurehead has been increased from $10m.
Researchers found more than 5,500 items ranging from mortar rounds to rockets and explosives.
The macabre discovery follows a suicide attack against a military base in the war-torn country.
The militants made the claim on social media.
Observers say the battle left Isis with 30 Russian tanks and surface-to-surface Grad missiles.
Recapture of Palmyra is reminder of threat the militant group still poses despite suffering setbacks.
Syrian regime and Russian forces will struggle to take back Raqqa and other terrorist strongholds.
The airbase is 100km (62 miles) away from the Syrian-government controlled city of Homs.
Pentagon official said the 50,000 figure was a 'conservative estimate'.
Isis propaganda and flags were seized by terror police at two addresses in Aschaffenburg and Mannheim.
Ramzan Kadyrov promises he will also personally join the fight if necessary.
Journalist John Cantlie was captured in Syria in 2012 and has appeared in several propaganda videos.
Islamic State has grown increasingly paranoid as senior commanders are killed.
UN says it has evidence Isis dishing out brutal punishments to civilians who reject their demands.
Australia's most senior Isis operative known as Abu Khaled al-Cambodi was reported dead twice in 2016.
Abdelilah Himich, also known as Abu Suleiman Al-Faransi, is believed to be living in Syria.
Christian militias liberating towns near Mosul find devastation in Iraq's largest monastery Mar Behnam.
Former Morrisons security guard Omar Hussain says he was shot whilst fighting with the Islamic State.
French-born Rachid Kassim is linked to several terror attacks in Europe and praised the Nice terror attack.
Campbell MacDiarmid and Razaw Salihy are guests on IBTimesUK's In the Field
Michele and Keith Harding have taken up the Kurdish struggle after their son Reece's death.