The war in Syria, which has involved pro-government, rebel and Islamist forces as well as other nations including Russia, the US, UK and Turkey, has seen hundreds of thousands killed.
Unicef said the last year of the conflict has been worse for Syrian children than the other five, with 652 killed.
Officials estimates suggest upwards of 400,000 people have died.
Anglican priest from Syria, Rev Nadim Nassar who founded the Resolution Foundation to highlight the plight of believers under pressure for their faith, told Premier's News Hour official estimates are probably very conservative.
He said: "Actually, I believe we've reached a million dead, and millions and millions of people - refugees [or] displaced. The country is shredded and bleeding...
"Most countries in the world are, unfortunately, involved directly or indirectly in this war including the UK, the US, Europe, Iran, Turkey, Russia, Israel. You name it, everybody is involved in this war in Syria."
Millions have been displaced, becoming refugees in neighbouring countries or making often dangerous journeys overseas for asylum instead.
Currently inside Syria it's thought a million civilians are still in besieged areas, caught between fighting among different groups.
At six years, the conflict has now lasted longer than World War II.
Politicians will be meeting in Brussels on April 5 to discuss further how to bring the war to an end.
Mairead Collins, Christian Aid's Advocacy Officer for Syria and Iraq, told Premier: "People need to pray and to put action behind their prayers, so that there's something done by leaders to actually take concrete action.
"They should take the opportunity of the upcoming Brussels conference to address the gaps around humanitarian access to places that are besieged... and also to listen to the voices of the Syrian civil society groups on the ground to ensure that they have a role in the future of Syria."
The Department for International Development has said Britain's given £2.3 billion since 2012 to help people in Syria and also in refugees camps in neighbouring countries. This has paid for over six million vaccinations, nearly five million medical examinations, more than six million emergency relief packages and more than 21 million monthly food supplies.
Listen to Premier's Alex Williams speaking to Nadim Nassar:
Listen to Premier's Aaron James speaking to Mairead Collins:
