MOSCOW (AP) -- Russia's dominant Kremlin-backed party appeared on course to retain the two-thirds majority in the parliament that allows it to change the constitution, results from 90% of the country's polling stations showed on Monday morning.

The election is widely seen as an important part of Russian President Vladimir Putin's efforts to cement his grip on power ahead of the 2024 presidential election, in which control of the State Duma, or parliament, will be key.

Results from about 90% of the country's polling stations gave the ruling United Russia party 49.65% of the vote for the 225 seats apportioned by party lists, according to the Central Election Commission. Another 225 lawmakers will be chosen by individual races, and the results on Monday morning showed United Russia candidates leading in 196 of those single-constituency districts.

Top United Russia official Andrei Turchak suggested Monday that the party will get 315 out of the 450 seats.

The results showed three other parties that almost always support Putin returning to the State Duma, as well as the New People party, which was formed last year and is regarded by many as a Kremlin-sponsored project.

Few opposition candidates were allowed to run for parliament this year after the Russian authorities unleashed a sweeping crackdown on Kremlin critics.

Organizations linked to imprisoned opposition leader Alexei Navalny have been declared extremist, and anyone associated with them was barred from seeking public office by a new law. Other prominent opposition politicians faced prosecution or were forced to leave the country under pressure from the authorities.

Navalny's team still hoped to make dents in United Russia's dominance with their Smart Voting strategy -- it promoted candidates who had the best chance at defeating those backed by the Kremlin. However, a massive effort by authorities to suppress the use of Smart Voting has been underway in recent weeks.

The government has blocked the Smart Voting website and pressured Apple and Google to remove an app featuring it from their Russian online stores. YouTube has also blocked several videos listing candidates endorsed by Smart Voting, and founder of the Russian messaging app Telegram Pavel Durov on Saturday blocked a Smart Voting chat bot set up by allies of Navalny.

The voting was also marred by numerous reports of violations, including ballot-stuffing, with some Kremlin critics saying that there were as many violations as in 2011, when reports of mass vote rigging in the parliamentary election triggered months of anti-government and anti-Putin protests.

The election this year was extended to three days, and in seven Russian regions voters were able to cast their ballots online. Officials cited coronavirus concerns and efforts to reduce crowding at the polls during a pandemic, but election monitors said that the measures left room for manipulating the results.

Fears of manipulations mounted on Monday morning, as the results of online voting in Moscow -- where approvals of the ruling party have always been particularly low and protest voting has been widespread -- were still not released to the public. The results in the other six regions have been released.

Nearly 2 million votes have been cast online in Moscow. "Where are the results of online voting (in Moscow)?" Navalny's close ally Lyubov Sobol wrote on Facebook. "They're not releasing them in order to rig more votes for United Russia candidates?"