"Russian forces, artillery and air defence units as well as command and control elements are still active in Ukraine," Stoltenberg said after talks with Latvian President Andris Berzins at the Blackheads House before heading to a meeting of EU Defense Ministers on the other side of the River Daugava.
"Russia has supported the separatists with forces, training and advanced weapons and there has been a steady buildup of tanks and armored vehicles across the border from Russia to Ukraine."
"I urge Russia to end its support for the separatists and to withdraw its forces and military equipment from Eastern Ukraine in accordance with the Minsk agreements," Stoltenberg said, while saying Minsk remained "the best opportunity for a lasting peaceful solution" to the crisis in Ukraine.
For his part, Berzins underscored the need for increased military spending, despite recent comments suggesting he did not think Latvia needed more troops.
"We are keenly aware that the safety and security-related issues are at the top of the Baltic and European agenda," Berzins said.
"We are strengthening the National Guard, law enforcement institutions, Border Guards and will take other measures that will significantly increase Latvian external and internal security."
Also paying a brief visit Wednesday was EU foreign policy supremo Federica Mogherini who said the introduction of fresh sanctions against Russia was not on the agenda.
"We will discuss and take some decisions about our common engagement in this challenging security environment around Europe with the defense ministers
"Our policy on sanctions is always the same, based on our unity... if the situation on the ground follows the commitments taken in Minsk last week obviously this will not be necessary. But we have to see the implementation happening... this is not something we are going to discuss today," Mogherini said.