"It is urgent, that the confronted parts, fulfill the international humanitarian laws, and guarantee the protection of innocent people who suffer, because of indiscriminating bombings and the shots," said O'Brien in a session of the UN Security Council that was analyzing the crisis in Yemen.
Since last year, Yemen, a bi-continental country with national territory in Africa and another part of its national territory in the Middle East, is having clashed between the government and rebel troops.
This conflict escalated in late March with anti-insurgent air strikes by a coalition led by Saudi Arabia.
According to O´Brien, the parties are responsible for civilian casualties, including more than 2,000 dead and wounded children.
At the meeting of the body with 15 members, chaired this month by Angola, the diplomat put recent examples of bombings of the foreign coalition against civilian targets.
"We recall the actors of the conflict that hospitals, schools and houses cannot suffer attacks, which is violated in Yemen, to the detriment of international humanitarian laws, this is unacceptable, O'Brien said in the Council via videoconference.
According to him, the humanitarian situation continues to deteriorate due to the lack of a political solution to the crisis, a scenario that terrorists exploit to increase their actions.
We demand that the parties ensure the protection of civilians and to facilitate humanitarian access to the victims, an issue hampered by the fighting and control points, it said.
O´Brien urged the Security Council and the international community to exert pressure to achieve this and to resume negotiations for the political solution of the crisis.
Regarding respect to assistance to the population, he explained that despite the continuation of the conflict, several agencies are making efforts to bring food, water and medicine to those affected.
United Nations estimates that 80 percent of the Yemeni population, about 21 million people, needs help.
In February, the world food program delivered food to three million humans, which represents a significant increase over the previous month, it was reported.
O´Brien recalled that it is running an annual plan of thousand 800 million dollars for humanitarian assistance.
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