Fighting has escalated in Aleppo in recent days.
The city, once Syria's commercial and industrial centre, has been divided roughly in two since 2012, with the government controlling the west and rebels the east.
Clashes have been reported in and around the northern Syrian city of Aleppo despite promises by Russia to halt military action to allow in aid.
More than 290,000 people have been killed and millions displaced in Syria's civil war, which began in 2011.
The EU's foreign affairs chief, Federica Mogherini, has condemned the latest upsurge in the civil war, saying: "The tragic images of children from Aleppo in Syria sadly show all too clearly the real human suffering of millions of people around the world caught up in humanitarian crises."
She added, "As the European Union, we have reiterated the urgent need for all parties to the conflict to restore the cessation of hostilities, ensure the lifting of all sieges and allow sustained, countrywide humanitarian access to those in need in Syria."
The EU says the escalation of violence in Aleppo, the continuous bombardments and the sieges that have put the lives of hundreds of thousands of Syrians in further danger and is hindering the efforts of the international community both to provide humanitarian aid and to support a political solution to the conflict.
Recalling that the Syrian authorities have the primary responsibility for the protection of its people, the Italian official said she "strongly condemns" all attacks against civilians and civilian infrastructure and the excessive and disproportionate attacks by the Syrian regime.
She said, "The EU believes that a Syrian led political transition, as supported by the International Syria Support Group (ISSG), endorsed unanimously by the United Nations Security Council (UNSC) and agreed in talks convened by the United Nations, is the only way of putting an end to more than five years of conflict in Syria.
"The EU will continue to do all in its power to ensure the full implementation of the Geneva communiqué and relevant UNSC resolutions. There is no military solution to the war and the ongoing escalation of violence has seriously put at risk the success of this process."
Mogherini added, "There will be no peace in Syria without a genuine political transition which is inclusive and representative of all Syrians.
"Once this transition has begun, the EU and its member states will be in a position to provide immediate support to Syria's reconstruction and also to help the return of refugees and the internally displaced to their communities."
S&D group Vice-Chair Enrique Guerrero Salom said, "We call on the United Nations and the European Union to promote campaigns to ensure all players, including non-state armed groups, are aware of their obligations under international law and to facilitate humanitarian assistance and protection for people under their influence."
His party colleague, Elena Valenciano, who chairs the European Parliament's subcommittee on human rights, said, "We stress the importance of improving security for aid workers and we urge the EU member states to call on the UN and the UN Security Council to guarantee the protection of both local and international humanitarian workers."