Malawi's ruling party dismissed on Tuesday claims that its supporters were behind an attack on protesters that has soured the run-up to September elections, as calls mounted for an investigation.

Unidentified men last week broke up a civil society demonstration of around a dozen people demanding an independent audit of the voters' roll and resignation of top electoral commission officials over fraud claims.

At least two demonstrators were hurt and two vehicles were torched in the attack in the capital, Lilongwe.

After condemnation from foreign diplomatic missions last week, Human Rights Watch said on Tuesday authorities "need to investigate this brutal attack on peaceful demonstrators and ensure that those responsible are appropriately punished."

'Fear and intimidation'

The investigation must include opposition claims that the 10-20 attackers – some masked and carrying sticks, pangas and heavy whips – had links to a youth militia aligned with the ruling Malawi Congress Party (MCP), it said.

"The MCP is being accused of using fear and intimidation against citizens expressing themselves in the lead-up to the September election," a statement said.

President Lazarus Chakwera will be seeking a second term to lead Malawi's 21 million people, nearly three-quarters of whom live in poverty.

MCP spokesperson Jessie Kabwila dismissed suggestions of party involvement. "We have never told our supporters to attack others," she said. "We challenge anyone making these allegations to provide evidence."

Ruling party says 'focused on winning election'

She accused the main opposition Democratic Progressive Party (DPP) of orchestrating the violence because of internal disputes.

"This was their own demonstration, and we have evidence they organised it," she said. "We are focused on winning this election based on our delivery, not violence."