Nazarbayev has held power since 1989 in Kazakhstan, which has attracted billions of dollars of Western, Russian and Chinese investment as production from its oilfields grows, but has never held a poll judged free and fair by Western monitors.
To applause in the Central Election Commission offices, chairman Onalsyn Zhumabekov said early results indicated Nazarbayev had won 91% of Sunday's ballot ,while the main opposition challenger Zharmakhan Tuyakbai had 6.64%.
Nazarbayev was due to appear at a stadium in Astana, capital of the ethnically diverse Central Asian country of only 15 million people, shortly after Monday's announcement.
The results tallied with most people's expectations, although they gave Nazarbayev nearly 8% more than the only exit poll carried out by a well-known pollster, a Gallup survey conducted with the International Republican Institute.
European observers are due to
give their assessment of the poll
Organisation for Security and Cooperation in Europe observers were due to give their assessment of the poll in the world's ninth largest country at 1000 GMT.
The main opposition For a Just Kazakhstan group has accused the West of putting oil before democracy.
Nazarbayev came to power as the Communist Party head of Kazakhstan, then won presidential elections in 1991 with 98.8% of the vote and in 1999 with 79.8%.
Tuyakbai's campaign team said on Sunday it had evidence of electoral fraud.
But the opposition says it will not break the law by organising demonstrations against the alleged vote-rigging like those that swept through Ukraine, Georgia and Kyrgyzstan and removed long-serving leaders.
Such protests were banned outright during the elections and require official permission at other times.
Tuyakbai's campaign team says
it has evidence of electoral fraud
Under Nazarbayev, Kazakhstan has reformed its economy and seen rapid growth due to oil production.
But it has also been plagued by corruption scandals, opposition parties have been closed down, and several politicians and an anti-corruption reporter have been jailed.
Nazarbayev says political and inter-ethnic stability for the Central Asian state during the turbulent post-Soviet years and fostering economic growth have been his main achievements.