Romania's ruling Social Democratic Party fired six ministers on Monday as the beleaguered party chairman sought to tighten his grip on the government.

Social Democrat chairman Liviu Dragnea has come under fire for his management style and corruption convictions, but has vowed to continue as party leader even though he can't be prime minister because of a conviction in 2016 for vote-rigging.

During a meeting, the party voted to fire the transport, economy, labor, culture, development, sports and communication ministers. Dragnea ally Lia Olguta Vasilescu switched from the labor to the transport ministry, while the others lost their ministerial posts. The defense minister resigned earlier Monday.

Premier Viorica Dancila said the changes were necessary because "we have to respond to new challenges ... both in the government and also as we (prepare) to take over the European Union presidency on Jan. 1."

Dancila, who has little executive power, thanked the previous ministers and explained why the party's new ministerial proposals were suitable.

Dragnea who effectively runs the government said Monday's decisions were "political and managerial."

He was handed a 3½-year sentence in June for abuse of power in office, which he has appealed.

In a boost for Dragnea, the party approved his ally, Codrin Stefanescu, as the new party secretary. He has been extremely critical about European Union commissioner Corina Cretu, a Romanian Social Democrat who has castigated the government for failing to absorb EU funds.

Earlier, Defense Minister Mihai Fifor and Bucharest Mayor Gabriela Firea resigned their positions to avoid being fired. Fifor said he would dedicate himself to helping the party win the 2020 parliamentary election.

Victor Ponta, a former prime minister and the party chairman before Dragnea, called the new government "a combination of professional incompetence, no backbone and unclean business with public money."

Firea, who has accused Dragnea of running the party in an underhand and arbitrary manner, resigned as acting leader of the party's Bucharest branch following reports that the party was poised to remove her. She later said she no longer held two other executive positions in the party.

"It is revenge," she said. "Dragnea wanted to get rid of me."