Conflicts around the world have led to some of the worst humanitarian catastrophes in recent years. Starvation, sexual violence and the displacement of millions has challenged geopolitical environments and prompted questions of how to respond to such emergencies.

Below is a list of the worst humanitarian crises around the world.

Yemen

The ongoing civil war in Yemen between government forces and Houthi rebels has killed thousands of Yemenis and displaced millions. More than 20 million -- 80 percent of the population -- are in need of humanitarian assistance, particularly relief from food insecurity.

Two-thirds of the country is at risk of starvation, according to the International Rescue Committee, a global humanitarian relief organization.

Exacerbating the conflict is a Saudi Arabian-led offensive against Iran-backed rebels. Saudi Arabia has been heavily criticized for airstrikes that have killed many civilians, destroyed key infrastructure and blocked Yemeni ports.

The rebels have block aid shipments in a bid to force agencies to give them control over humanitarian efforts.

The Saudis began its military intervention in an effort to restore former President Abdu Rabbu Mansour Hadi to power. The country was already the Arab world's poorest when the conflict began in 2015.

Syria

What started as part of a broader movement in 2011 to usher in democratic reforms has turned into a deadly conflict that has killed more than 500,000 people and resulted in millions of Syrians risking their lives to escape the violence.

Brutal fighting between forces loyal to President Bashar al-Assad, opposition forces and extremist militants, including the Islamic State, has left some 12 million people in need of aid, the IRC reported.

Turkish and Kurdish-led forces have exacerbated the conflict in northern Syria.

The Democratic Republic of Congo

The central African nation has been engulfed in a rash of conflicts between government forces and local militias. The fighting has left millions displaced and dead.

In addition, Africa's largest nation has one of the highest rates of sexual violence in the world. Reports include babies being burned alive and women being raped upward of 150 times.

Congolese warlord Bosco Ntaganda, known as "The Terminator," was sentenced in November to 30 years in prison for war crimes and crimes against humanity for his role in numerous atrocities in the mineral-rich country from 2002-03.

South Sudan

Born out of decades of civil war, South Sudan plunged into extreme violence following its independence from Sudan. More than 2 million have fled the country and another 2 million have been displaced.

Five million are at risk of starvation, which could increase as locust swarms could destroy crops, the IRC reported. Many are unable to feed their families and lack access to jobs and an education.

Women are often at risk of becoming victims of sexual violence.

Venezuela

Nearly a quarter of Venezuelans are in need of humanitarian assistance amid Inflation and political instability.

Many have fled to neighboring South American countries and shortages of food, water and medicine have created unrest. The Trump administration imposed sanctions on the regime of Nicols Maduro in an effort to force out the socialist leader.

The Associated Press contributed to this report.