Sunday's presidential election in Kazakhstan failed to meet international democratic standards, Europe's main poll-monitoring body the OSCE has said.
The OSCE says Mr Nazarbayev's victory was not won fairly
Failings included ballot box stuffing, intimidation of the opposition, and media bias, the OSCE said.
It said its 460 monitors had noted some improvements from previous elections, but flaws "limited the possibility for a meaningful competition".
President Nursultan Nazarbayev, in power since 1989, won 91% of the vote.
OSCE CRITICISM OF POLL
Restrictions on campaigning
Limits on political discourse
Media bias in favour of incumbent
Pressure on students to vote for incumbent
Harassment of opposition campaign staff
Multiple voting and ballot box stuffing
Overcrowding at polling stations hindered voting process
Electronic voting system undermined public confidence
"Regrettably, despite some efforts which were undertaken to improve the process, the authorities did not exhibit sufficient political will to hold a genuinely good election," said Bruce George, co-ordinator for observers from the Organization for Security and Co-operation in Europe.
In a strongly-worded statement, the OSCE said: "The voting was generally calm and peaceful, but the process deteriorated during the count, which was viewed as bad or very bad in one out of four counts observed.
"Unauthorised persons interfering in polling stations, cases of multiple voting, ballot box stuffing and pressure on students to vote were observed during voting and during the count, observers saw tampering with result protocols and a wide range of procedural violations," it said.
Main opposition candidate Zharmakhan Tuyakbai, who secured just 6.64% of the vote according to official results, alleged there had been "multiple violations".
"We will take all legal measures to protest the official results of the voting and will press for this election to be declared invalid," Mr Tuyakbai said on Monday.
"The authoritarian regime of Nazarbayev is taking a totalitarian turn," he said.
But President Nazarbayev insisted that the results demonstrated the population's craving for the status quo.
"We're talking not about revolutions but evolutions," he told reporters. "Kazakhstan voted for calmness and stability."
The Kazakh poll was closely watched because elections in some other former Soviet Union republics - Georgia, Ukraine and Kyrgyzstan - led to uprisings which overthrew their rulers.
However, Mr Nazarbayev pledged to pursue political reform during his next seven years in power.
The president also said - before the election - that his goal was for Kazakhstan to hold the OSCE presidency in 2009.
Correspondents say the body's negative assessment of Sunday's election will not help his case.