AGARTALA: The ruling BJP workers clashed with activists of ally IPFT and opposition Congress at two places of Tripura since Monday over submission of nomination papers for the coming by-polls in panchayat bodies.Altogether 21 political workers and policemen were injured in the two clashes that occurred in West Tripura and Sipahijala districts, police said.Workers of the BJP and its ally Indigenous Peoples Front of Tripura (IPFT) clashed at Boxanagar in Sipahijala district Monday over submission of nomination papers.The BJP and the IPFT have announced to contest the panchayat by-polls and the next Lok Sabha polls separately.Sipahijala SP Kulwant Singh said, "We dispersed the mob after a lathi charge and bursting of tear gas shells."Sub-divisional Magistrate Saju Vaheed said, altogether 13 persons - Sonamura Sub-Divisional Police Officer Rajdip Deb, one CRPF man, six IPFT supporters and five BJP supporters - were injured.The IPFT charged the BJP with attacking its cadres while the saffron party denied the allegation."We are in an alliance with BJP in the state government. After mutual consultation, we went to submit nomination papers at Boxanagar. Some BJP leaders stopped us on our way. Later BJP supporters attacked us with stones, bombs, sticks. Many of us were injured," Youth IPFT president Shuklacharan Noatia claimed.BJP spokesperson Mrinal Kanti Deb, however, said the party was not involved in any attack on the IPFT."The IPFT is our ally in state government. There is no strain in the relationship. We also believe in friendly, democratic electoral exercise and have not attacked Congress supporters. These are baseless allegations," Deb said.He said these "local issues" would not affect the BJP's alliance with the IPFT in the government.In the other clash Tuesday, two groups of the BJP and the Congress clashed near the Dukli Rural Development block, about 12 km from here, and the police lobbed tear gas shells and resorted to lathi charge to disperse them.Amtali SDPO Ajay Kumar Das said the trouble started at shortly after 12 noon when supporters of the two parties were engaged in a fight over submission of nominations."At least eight persons including two policemen were injured. One of them received injuries on the head," Das said.Tripura Pradesh Congress president Birajit Sinha alleged that BJP supporters had attacked his partymen.Over 3,000 seats of gram panchayat, panchayat samiti and zilla parishad have become vacant after elected public representatives resigned since the BJP-IPFT government assumed office on March 9 this year.The by-elections would be held on September 30.