"The European Parliament has backed calls for EU enforcement tools to be prepared, which will put pressure on Russia to comply with the UN Security Council resolutions they have signed. The indiscriminate use of chemical weapons and barrel bombs against civilians in Aleppo must end," the letter, sent by the European People’s Party (EPP), the Alliance for Liberals and Democrats for Europe (ALDE) and the Greens/European Free Alliance (Greens/EFA), said.
It also noted that the European Union needs "a tougher sanctions regime targeting Putin and his inner circle is the most efficient way."
Earlier in October, different European politicians, including Germany's special coordinator for Russia policy Gernot Erler brought the idea of introducing restrictions against Russia over the worsening humanitarian situation in Syria's Aleppo.
On Sunday, the United Kingdom, the United States and France discussed putting pressure on Russia, including sanctions, to convince it to change its policy on Syria.
The Russian Aerospace Forces began their operation against terrorists in Syria on September 30, 2015, at the request of Syrian President Bashar Assad.