Hundreds of opposition supporters and farmers on Thursday protested the Sri Lankan government's plan to lease a southern seaport to a Chinese-controlled joint venture in exchange for the heavy loans to build the port.

The protesters led by Marxist party People's Liberation Front said the proposed partnership is akin to a sellout of the country.

The government wants to lease the loss-making port to a joint venture company in which China will have 80 per cent ownership. The lease period will be 99 years.

The government also proposes to lease 15,000 acres (6,070 hectares) in Hambantota district and adjoining Moneragala district for an industrial zone.

Protesters carried placards that read "hands off our lands" or "Stop selling Hambantota port." 

D K Sumathipala said farmlands are at risk of being taken over for the industrial zone and he was determined to fight.

"We are farmers; we can't move out of our lands," he said.

"I was born here, we have nowhere to go," said Premawathie Samarasekara, also a farmer. "We will not give away our lands to the Chinese," she said.

Prime Minister Ranil Wickremesinghe told a gathering on Thursday that private lands will not be taken over for the industrial zone. He said the partnership was the only way to free the country from the debt burden.

China invested over $1.2 billion in the Hambantota port in what some analysts call its "string of pearls" strategy in countries surrounding India.

Sri Lanka's government criticised the project before being elected in 2015 but later approached China seeking help to make it viable.