Thousands of farmers in tractor convoys have burst through police barricades to take their protest against new farm laws to the heart of India’s capital as the nation was marking Republic Day with a military parade.

Police had sealed most entrances to the city with containers and trucks earlier on Tuesday and resorted to tear gas and batons as the farmers broke through.

Some protesters reached a major intersection 3km (1.8 miles) from where Prime Minister Narendra Modi and other government leaders watched tanks and troops parade past and fighter jets fly overhead.

Modi waved to crowds and sent out Twitter greetings for the national holiday without mentioning the farmers.

He was driven back to his residence before any personal confrontation with the farmers, the biggest challenge his Hindu nationalist government has faced in its six years in power.

Authorities had agreed to let the farmers stage a tractor rally as long as they waited for the official Republic Day parade to end.

But flag-waving protesters on at least four major arteries climbed over or just pushed aside the barricades and concrete blocks and pressed on into the city.

Tens of thousands of farmers have camped on the outskirts of the capital since November, protesting against new laws which deregulate produce markets.

Union leaders say the laws will allow private Indian conglomerates to take over the agriculture sector – the bedrock of the economy – displacing the existent system of purchases by the government at guaranteed prices.

Smaller farmer demonstrations were also held in other cities, including Mumbai and Bengaluru.