Patna, Aug 17 (IANS): Former Bihar chief minister Nitish Kumar Sunday said the Bharatiya Janata Party (BJP) was a party of rumour mongers.

"The BJP is a party of rumour mongers," he said at a rally ahead of a by-election in Chapra assembly constituency in Bihar's Saran district.

Nitish Kumar, also a senior Janata Dal-United leader, said Narendra Modi has become the prime minister by using his "poisonous propaganda" during and before the last Lok Sabha polls.

"Alliance of the JD-U, the Rashtriya Janata Dal and the Congress is to check communal forces in the country and it is the only medicine for the BJP in Bihar," he said.

He said he and RJD chief Lalu Prasad came together to check those spreading hatred and poisonous propaganda.

Addressing the rally, Lalu Prasad accused Modi of betraying the people by not fulfulling the promises made during the election campaigning. "We have joined hands in view of the dangerous designs of the BJP," he said.

Last week, Lalu Prasad and Nitish Kumar came together at an election rally in Hajipur assembly constituency for the first time in two decades.

Ten assembly seats in Bihar will go for by-elections Aug 21.