(CNN) This holiday week erupted in an extraordinarily violent start, with high-profile attacks in four cities on Sunday and Monday.

At least 75 people were killed in the incidents, which are not connected.

KARAK, JORDAN

Jordanian mourners carry the coffin of Ibrahim Bashbsha, a day after he died in the attack.

Attackers armed with machine guns and hand grenades entered Karak Castle, a tourist attraction, and killed 10 people and injured 34 on Sunday.

Who: ISIS claimed responsibility for the attack, which was carried out by four men. They were killed.

Also: This was the first time a civilian target was hit by a terrorist attack in Jordan in more than a decade.

Jordanian security forces patrol around the Crusader castle on December 19, 2016 in Karak.

ADEN, YEMEN

Yemenis gather at al-Sawlaba base in Aden's al-Arish district after a suicide bomber targeted a crowd of soldiers.

What happened: At least 52 soldiers were killed and 34 were injured in a suicide bombing on Sunday in the Southern Yemeni city of Aden.

Who: ISIS claimed responsibility.

Also: At least 48 soldiers were killed on December 10 at the same camp. The attackers targeted soldiers who were lining up for pay, according to news agency Saba. ISIS claimed responsibility for that attack as well.

BERLIN, GERMANY

JUST WATCHED Germany mourns after attack in Berlin Replay More Videos ... MUST WATCH Germany mourns after attack in Berlin 00:50

What happened: of shoppers at a Christmas market on Monday, killing 12 and wounding 48. A truck crashed into a crowd of shoppers at a Christmas market on Monday, killing 12 and wounding 48.

Who: There is a manhunt underway for the attacker. ISIS-affiliated Amaq news agency has released a statement saying the attack in Berlin was carried out by "a soldier of the Islamic state."

Also: This was similar to a July attack in Nice, France when a truck drove into a crowd on Bastille Day, killing 86 and injured more than 200. Terror groups have encouraged followers in the West to use vehicles in attacks.

Photos: Berlin attack aftermath The Brandenburg Gate in Berlin is illuminated in the colors of the German flag on Tuesday, December 20, one day after a truck crashed into a crowded Christmas market there. At least 12 people were killed and 48 injured in what police are investigating as a terrorist attack. Hide Caption 1 of 13 Photos: Berlin attack aftermath A police officer places a candle at a makeshift memorial in Berlin on December 20. Hide Caption 2 of 13 Photos: Berlin attack aftermath A woman is illuminated by candles as she cries in Berlin on December 20. Hide Caption 3 of 13 Photos: Berlin attack aftermath A man prays at a Berlin memorial on December 20. Hide Caption 4 of 13 Photos: Berlin attack aftermath German Chancellor Angela Merkel lays flowers at the memorial on December 20. She is joined by, from left, Berlin Mayor Michael Muller, Minister of the Interior Thomas de Maiziere and Foreign Minister Frank-Walter Steinmeier. Hide Caption 5 of 13 Photos: Berlin attack aftermath Merkel, bottom left, views the scene of the attack. Hide Caption 6 of 13 Photos: Berlin attack aftermath A woman reacts near the crime scene on December 20. Hide Caption 7 of 13 Photos: Berlin attack aftermath Mourners gather at the Kaiser Wilhelm Memorial Church near the crash site. Hide Caption 8 of 13 Photos: Berlin attack aftermath A police officer holds her weapon near the market. Hide Caption 9 of 13 Photos: Berlin attack aftermath A woman lays flowers at a makeshift memorial across from the market. Hide Caption 10 of 13 Photos: Berlin attack aftermath A stall worker is comforted in the market area on December 20. Hide Caption 11 of 13 Photos: Berlin attack aftermath People attend a memorial service at St. Hedwig Cathedral in Berlin on December 20. Hide Caption 12 of 13 Photos: Berlin attack aftermath A police van drives by Christmas decorations at a Christmas market in Frankfurt, Germany, on December 20. Police presence has been stepped up at Christmas markets across Germany following the attack in Berlin. Hide Caption 13 of 13

ANKARA, TURKEY

JUST WATCHED Graphic video: Russian ambassador shot Replay More Videos ... MUST WATCH Graphic video: Russian ambassador shot 00:10

Who: The man who opened fire on the ambassador was identified as Mevlut Mert Altintas, 22, a Turkish police officer. He was killed.

Also: Russia and Turkey called it a provocative terror attack. The gunman shouted "Allahu akbar (God is greatest). Do not forget Aleppo! Do not forget Syria!" Russian President Vladimir Putin said the killing was aimed at undermining normalization of Russian-Turkish relations, as well as the "peace process in Syria." Human rights groups and other countries have denounced Russia over its backing of the Syrian leader.