A day after clashes ended with an agreement that the farmers could demonstrate in the capital, tensions rose again in the protests over laws that farmers fear could rob them of minimum guaranteed prices for their produce.

Farmers who arrived in trucks, buses and tractors at Delhi's Singhu border with Haryana state on Friday, blocked the main northern highway into the capital on Saturday morning, chanting slogans against Prime Minister Narendra Modi's government and waved the red, yellow and green flags of farmer's unions.

They appeared ready for a long sit-in and refused to relocate to a designated protest site, raising fears of fresh clashes between security forces and protesters.

On Friday, police fired tear gas and water cannons to disperse the protesters before letting them march into the capital and stage a protest at a designated site.

Both security forces and farmers have installed barricades to prevent a repeat of Friday's clashes.

Opposition Congress Party leader Rahul Gandhi also slammed the government.

"Our slogan was, 'Hail the Soldier, Hail the Farmer,' but today PM Modi's arrogance made the soldier stand against the farmer. This is very dangerous," Gandhi tweeted in reaction to a photo of a policeman attempting to hit a farmer with a baton.

Modi's laws, enacted in September, let farmers sell their produce anywhere, including to big corporate buyers like Walmart Inc, not just at government-regulated wholesale markets where growers are assured of a minimum procurement price.

But many small growers worry they will be left vulnerable to big business and could eventually lose the price supports for key staples such as wheat and rice.

The government says there is no plan to eliminate wholesale markets and that farmers have the choice of buyers.

It hopes the deregulation attracts agricultural investment and fixes supply chains that lose one-fourth of India's produce to wastage.

Australian Associated Press