The explosion happened at around 10am local time (8am GMT).
The Syrian army reportedly sent additional troops to Palmyra, diverting personnel from Aleppo.
No group has claimed responsibility for the blast but al-Shabab frequently carries out such attacks.
Daesh fighters have entered from the north and west of the city, according to activists.
The attack 'bore the hallmarks of al-Qaeda', although Islamic State also have a presence in the port city.
Pentagon official said the 50,000 figure was a 'conservative estimate'.
Defense Secretary Ash Carter said 'sooner we crush ISIL's barbaric ideology, the safer we'll all be'.
De Mistura says the only way to win peace in Syria was to reach a power-sharing agreement between rival factions.
IBTimes UK Special Report: The fighters ride to battle under wooden crucifixes and Shia paramilitary flags
Man had a large image of the Islamic State flag in his home.
Boko Haram renowned for forcing civilians on suicide bombing missions in crowed areas like Madagali market.
EXCLUSIVE: IBTimes UK interviews government body and teachers union on unrest in Cameroon's Anglophone areas.
Mysterious crates were allegedly stashed on board the vessel before it was sunk by Soviet torpedoes.
The 11th century minaret at the mosque was destroyed three years ago and sections of the medieval souk were burned down.
End goal is "to weaken or destabilise the Federal Republic of Germany," said Hans-Georg Maassen.
The bomb was reportedly placed in a bin at a security checkpoint near the tourist site.
There are around 9,800 US military personnel in Afghanistan training security forces battling Taliban.
Regime is however still struggling to target larger ballistic missiles.
The group said that it believed it had less than 48 hours to remove its volunteers from the rebel-held region.
The troops withdrew after being attacked by suicide car bombs and heavy enemy fire.
The waiver will allow exceptions from provisions in the four-decades-old Arms Export Control Act.
Ramzan Kadyrov promises he will also personally join the fight if necessary.
Phil Shiner, formerly of Public Interest Lawyers, faces being struck off.
Sergey Lavrov says Moscow and Washington will hold discussions on Saturday.
Committee to Protect Journalists urges Kiir's government to reverse decision and 'stop harassing journalists'.
"The risks at stake are profound and represent a fundamental threat to our sovereignty," Alex Younger said.
Fewer than 200 survivors of the attacks on Pearl Harbor and other military bases in Hawaii are alive today.
Centcom said Iraqis had sought aerial support after being subjected to continuous fire from Daesh militants.
US General John Nicholson had pointed out the connection between the insurgents, Russia and Iran.
Journalist John Cantlie was captured in Syria in 2012 and has appeared in several propaganda videos.