Kyrgyzstan’s Prime Minister Kubatbek Boronov has stepped down after the Central Electoral Commission annulled the results of Sunday’s parliamentary elections in response to accusations of vote-rigging.

Boronov and Dastan Jumabekov, the speaker of the country’s parliament, presented their resignation letters at a meeting of legislators in Bishkek.

At an emergency session the parliament appointed Sadyr Zhaparov, a founder of the opposition Mekenchil party, which had lost the election, as acting prime minister.

Earlier on Tuesday, Zhaparov had been released by protesters from prison, where he was serving a sentence of 11 years and six months for taking a government official hostage in 2013.