President Dmitry Medvedev and prime minister Vladimir Putin give their reactions to preliminary election results Reuters

Vladimir Putin's United Russia party is scrambling to come to terms with an election outcome that showed its support severely dropping across the country.

With 95% of votes counted, the party stood to take 49.67% in Sunday's parliamentary election. Election monitors from opposition parties and from independent NGO Golos complained of widespread falsifications, meaning the party's true support was possibly far lower.

The result registered Russians' increasing suspicions of Putin's authoritarianism, ingrained corruption and falling living standards. Solidarity, an umbrella opposition group, called a protest for 7pm local time (3pm GMT). Riot police and interior ministry troops continued to patrol parts of Moscow on Monday.

The parliamentary vote was the biggest test of public opinion following Putin's announcement earlier this year that he plans to stand for the presidency in a March 2012 election.

Voters dealt United Russia, founded with the sole purpose of supporting Putin, a harsh blow. The party is expected to lose 77 seats in the Duma, dropping from 315 to 238. It failed to break through the important 50% barrier in the popular vote – a big drop from the more than 64% popular support it garnered in the country's last election in 2007. Yet it will still retain a majority in the 450-seat chamber.

United Russia was forced to deny rumours that Boris Gryzlov, party chairman and speaker of the Duma, would resign following the result.

"We are quite satisfied with the speaker who we currently have," Sergei Neverov, a top party official, told journalists on Monday. "Today we can confidently say that the United Russia party received the moral right to continue the course of President Dmitry Medvedev and Prime Minister Vladimir Putin," he said.

Another party official sought to put to rest worries that the result could put into doubt Putin's victory in the presidential vote set for 4 March. "As soon as we lose our confidence, we have nothing to do," Andrei Vorobyov, chairman of the party's central executive committee, told journalists.

"These 10 years [that Putin has been in power], it is very easy to lose confidence, but today it is at a very high level," he said. "Our candidate is known – it is Putin, our leader, and we will do everything in our power to ensure that our candidate wins in the first round."

Results showed that Putin's party reached a low in the region of Yaroslavl, taking just 29% of the vote. It got a boost, however, in Chechnya, which is ruled by ruthless leader Ramzan Kadyrov. With nearly 100% of voters turning out, United Russia took 99.48% of the vote, results showed. It also took more than 90% in neighbouring Dagestan.

The New Region newspaper noted that "the record in central Russia was brought by patients of psychiatric clinics, who gave more than 90% of votes to United Russia".

Russians continued to register cases of falsification through the night and into Monday. News reports on state-run television appeared to show results that implied turnout in some regions was as high as 146%.

Vorobyov, the United Russia official, said the party would seek to form a coalition with the other three parties that made it into the Duma – the Communists, the far-right LDPR and Just Russia. All three have long collaborated with the Kremlin. The liberal Yabloko party, which failed to reach the threshold to enter the Duma, said it would challenge the election results.