Thousands of party cadres and activists of feeder outfits gathered in all the 14 districts across the state as part of the first phase of stir in identifying land to be taken over by the government.
Addressing the agitators at Vadakkanchery in Thrissur district, CPI(M) state secretary Pinarayi Vijayan said the stir would be intensified if the UDF government refrained from retrieving the land identified by the campaigners.
Vijayan said there had been concerted efforts by "land mafia" with the support of the government to sabotage the land reform legislation, which set ceiling of 15 acres for non-plantation land to be possessed by a family.
He said the move to upset the legislation that restricted reclamation of paddy fields and wetlands was also a matter of grave concern.
Senior CPI(M) leaders, including state opposition leader V S Achuthanandan, also addressed the campaigners in different parts of the state.
Party leaders claimed that about one lakh people had lined up for the campaign being carried out with participation of the party's feeder outfits like farmers and farm workers unions and scheduled caste and scheduled tribes' units.