Agra/Greater Noida, May 8 (PTI) Farmers' unrest over land acquisition today spread to Agra, where protesters clashed with police and torched vehicles, even as the toll in Greater Noida violence climbed to four while UP police announced a reward for arrest of a farmer leader for allegedly inciting the agitators.

Four policemen were injured in Chaugaan village in Agra when farmers turned violent and clashed with police demanding higher compensation for their land acquired for Yamuna Expressway.

"Four policemen were injured when farmers turned violent during a protest and indulged into arson," Special Director General of Police (Law and Order) Brij Lal said in Lucknow, adding irate villagers torched several vehicles and tents at the construction site.

A protester, identified as Kalu, injured in yesterday's clashes between police and farmers at Bhatta Parsaul village in Gautam Buddha Nagar district, a Delhi suburb, died, taking the toll to four in the violence.