Three AAP MPs from Delhi and Union Minister Hardip Puri from the BJP on Monday took oath as Rajya Sabha members.
The first to take the oath was Puri, who was elected from Uttar Pradesh. Three AAP MPs - Sanjay Singh, N D Gupta and Sushil Gupta - also took the oath.
Sushil Gupta took oath in English, while the others took oath in Hindi when the Rajya Sabha assembled after President Ram Nath Kovind's customary address to the joint sitting of Parliament.
Before the House started a business, Prime Minister Narendra Modi walked up to the Opposition benches and greeted leaders from the Opposition.
He shook hands with former prime minister Manmohan Singh, Leader of Opposition Ghulam Nazi Azad, former defence minister A K Antony and NCP chief Sharad Pawar.
Modi, who was accompanied by Parliamentary Affairs Minister Ananth Kumar, also greeted CPM leader T K Rangarajan, Ram Chandra Prasad Singh (JD(U)), Dilip Tirkey (BJD) and Motilal Vora (Congress).
The new AAP MPs, who sat on a dharna at the Gandhi statue inside Parliament House complex against FDI in retail and sealing of commercial establishments in the capital earlier in the day, were also greeted by several Opposition members and Law Minister Ravishankar Prasad.