Estonia's foreign minister says Russia's response to the row over a Soviet war memorial is an "attack" on the whole European Union.
Estonia says its Moscow embassy is "under siege"
Minister Urmas Paet said Russia had launched real, psychological and - via the internet - virtual attacks since Estonia decided to relocate the statue.
Mr Paet called for a "vigorous" EU reaction to Moscow.
Estonians of Russian origin rioted last week in protest at the decision to move the statue of a Red Army soldier.
One person died and 153 were injured in the unrest.
On Monday, Russian MPs paid their respects at the controversial monument which was re-erected on Monday at a military cemetery in Tallinn, away from the city centre.
Estonians say the soldier symbolised Soviet occupation. Russians describe it as a tribute to those who fought the Nazis.
In a statement issued on Tuesday evening, Mr Paet protested against what he said were "co-ordinated activities undertaken against Estonia by Russia" in response to the row.
1918: Estonia gained independence from Russia
1940: Forcibly incorporated into Soviet Union
1941-1944: Occupied by Nazi Germany
1944: Soviets return as Nazis retreat
1991: Gains independence as Soviet Union collapses
1994: Last Russian forces leave Estonia
Now: Ethnic Russians make up quarter of Estonia's 1.3m people
He said "cyber terrorists'" attacks against internet pages of Estonian government agencies and the office of the President had originated from Russian government computers.
Russian youth organisation "Nashi" has laid a siege to the Estonian embassy in Moscow, he said, accusing the Kremlin of paying the demonstrators.
"We find it necessary that the reaction on behalf of the European Union to the behaviour of Russia should be as vigorous as possible," he said.
"This could mean suspending different talks between the European Union and Russia or not commencing them at all. The postponement of the European Union - Russia summit should be also given full consideration."
Reports said Russian police scuffled with pro-Kremlin youth activists outside the Estonian embassy on Wednesday, arresting one person as protestors attempted to prevent diplomats entering or leaving the building.
Tensions have escalated ahead of the World War II Victory Day anniversary on 9 May.
The anniversary is traditionally a day of patriotism and pride for many Russians.
Moscow Mayor Yuri Luzhkov called for "a boycott of all things connected with Estonia," at a May Day rally on Tuesday.
He said Estonia had dismantled the Soviet memorial "in the most barbaric way".
More than a quarter of Estonia's 1.3m people are ethnically Russian, and speak Russian.
However, half of them do not have Estonian citizenship.
During the years of Soviet occupation after the war tens of thousands of Estonians were killed. They say their country was effectively colonised, with many Russians being brought in as workers and military personnel.