Tanzania's national electoral commission on Saturday accepted the nomination papers of Luhaga Mpina, a senior politician from the second largest opposition party, enabling him to contest next month's presidential election following a court order.

A high court ruling on Thursday overturned a previous decision by the Independent National Electoral Commission (INEC) that had prevented Mpina from lodging his electoral nomination papers after he was disqualified.

His disqualification meant incumbent President Samia Suluhu Hassan, who has been in office since March 2021, would potentially face opposition only from smaller parties in the October 29 election.

Mpina, who is the top candidate for the Alliance for Change and Transparency (ACT-Wazalendo) party, successfully challenged the decision to disqualify him by the Office of Registrar of Political Parties, citing complaints that his party had failed to comply with nomination procedures.

Addressing a media briefing after lodging his nomination papers, Mpina said political parties were constitutionally guaranteed to operate in the East African country.

"Opposition politicians and opposition parties are not treasonous and criminals. There is no need to use authorities to punish political parties," Mpina said in the capital Dar es Salaam.

Earlier on Saturday, the chairperson of INEC accepted his nomination as presidential candidate for ACT-Wazalendo.

Opposition parties face an uphill battle trying to dislodge Hassan and her ruling Chama cha Mapinduzi (CCM) party, amid a government crackdown on rivals.

Leading opposition party CHADEMA was disqualified in April from contesting the election after failing to sign the electoral code of conduct as part of its call for reforms.

Party chairperson Tundu Lissu is in jail after being charged with treason amid criticism of Hassan's human rights record.

Hassan has denied the accusations and said her government was committed to protecting human rights.