Rashtriya Janata Dal president Lalu Prasad on Monday teased Union Home Minister Amit Shah by recalling a 2015 incident when the then BJP chief was trapped inside an elevator at Patna.

Prasad was reacting to Shah's speech at a rally in Paliganj near here two days ago when the BJP leader had charged the RJD with patronising land grabbers and vowed to "straighten them by hanging them upside down".

"Had he not got stuck inside a lift? He will be trapped again", Prasad told reporters, evoking guffaws from supporters.

The allusion was to an episode in 2015 when Shah was in Bihar to oversee his party's preparedness for the assembly elections.

Late in the night, Shah had returned to the state guest house and taken the elevator which got stuck, trapping him and a number of other BJP leaders inside for close to half an hour before technicians set the lift right.

Prasad was speaking to reporters at the Vidhan Sabha premises here, when his wife Rabri Devi, three other candidates of RJD and one of ally CPI(ML) Liberation filed nomination papers for election to the state Legislative Council.

Incidentally, the BJP and its allies were trounced in the 2015 assembly polls while the Mahagathbandhan, which then comprised RJD, Chief Minister Nitish Kumar's JD(U) and Congress, won hands down.

The JD(U) boss is back in the BJP-led NDA, having dumped Mahagathbandhan a couple of months ago for the second time in six years.

State BJP president Samrat Choudhary expressed disgust when his attention was drawn to the RJD supremo's barb at the Home Minister.

"Lalu Prasad has been in politics for decades. But never ever has he said anything that could be taken seriously", said Choudhary, who is also a Deputy Chief Minister.