US President Barack Obama has said that he is building a US-led coalition that will "dismantle this network of death" created by jihadists in the Middle East, in his address at the United Nations General Assembly.

Obama told world leaders that the "only language understood by killers like this is the language of force" and that "the future belongs to those who build, not those who destroy".

He warned militants who have joined the ranks of Isis (now known as the Islamic State) to "leave the battlefield while they can."

The American leader said that the United States will be a "respectful and constructive partner" in its support for Iraqis and Syrians to maintain their communities in the face of the threat from the Islamic State.

"Ultimately, the task of rejecting sectarianism and extremism is a generational task — a task for the people of the Middle East themselves," Obama said. "No external power can bring about a transformation of hearts and minds."

He declared that the world was at a "crossroads between war and peace" as jihadist groups continue to cause instability across the region.

The strikes in Syria by the US-led coalition have killed at least 70 IS militants, 50 al-Qaida-linked fighters and eight civilians, according to activists.

The United States has conducted over 200 air strikes on the group's positions in Iraq since August 2014, while Saudi Arabia, the United Arab Emirates, Jordan, Bahrain and Qatar have joined or supported the strikes in Syria.

The Nobel Peace Prize winner also spoke of the threat of Ebola in West Africa; Ukraine's journey towards democracy in light of Russia's role in the unrest seen in the former Soviet republic's eastern regions; and the continuing Israeli-Palestinian conflict.