Nearly 90 percent of voters supported Syria’s new constitution meant to end decades of one-party rule, state TV said on Monday.
With a turnout of 57.4 percent, 89.4 percent voted in a referendum promising constitutional changes to presidential terms and governing bodies, which the United States labeled a "sham" and "laughable."
The opposition had called for a boycott of the referendum.
The announcement came just after the European Union adopted sanctions on Syria’s central bank and froze the assets of several Syrian government officials.
Under the new charter, the country’s political system would be based on "pluralism", although it would ban the formation of parties on religious lines.
It also stipulates that the president can be elected for two seven-year terms, but another article says these conditions only take effect after the next election for a head of state, set for 2014.
This means that Assad could in theory stay in power for another 16 years.
Russia welcomes Syria's referendum as a step toward democracy, Russia's Foreign Minister Sergei Lavrov said.
The Russian Foreign Ministry said the referendum confirmed popular support for the Syrian government’s course toward “turning Syria into a modern democratic state, expanding the rights and freedoms of its citizens.”