Protesters on Saturday night demanded President Viktor Yanukovych's resignation over his decision to snub the agreement, in favour of closer ties with Moscow.
Al Jazeera's Jennifer Glasse, reporting from Kiev, said the protesters are gearing up for a larger protest planned on Sunday.
"This protest is in full strength and the numbers are growing," Glasse said.
"The real question is, how many people will show up on Sunday, when organisers have asked them to come out in big numbers.
Organisers also vowed to stay at the square "for as long as it takes" to get what they want from President Yanukovych, she said.
President Yanukovych have so far rejected their demands.
Last Tuesday, he signed an agreement with Russian Vladimir Putin, for Russia to buy $15 billion of Ukrainian bonds and to reduce by about one-third the price it pays for Russian gas supplies.
The rallies were galvanised by a brutal police action to disperse the demonstrators on the capital's main square on November 30th, and the number of protesters reached hundreds of thousands.
On Friday, the country's top prosecutor defended the police actions against the protesters.
General Viktor Pshonka sought to turn the tables on the opposition, saying radical nationalist groups were to blame for provocations on the square.
However, his comments came a day after parliament passed a bill granting amnesty to the anti-government demonstrators arrested during the government crackdown on November 30th.
That has led some protesters like Vasyl Voznyak to believe momentum is beginning to turn, however gradually.
"We're waiting for some positive movements, they are going very slowly," he said.
"There was a decision for amnesty of our arrested guys, another decision will come soon to stop political chasing. There are some achievements."
German Chancellor Angela Merkel has also now added her voice to those calling for the peaceful protests to continue with no further threat of a crackdown.
Source: Al Jazeera