PM Modi tweeted: "Today, we pay homage to the brave personnel who sacrificed their lives while protecting our Parliament.
"Their martyrdom will never be forgotten." It got 755 retweets and 4K likes.
Lok Sabha Speaker Om Birla wrote: "Paid homage to the martyrs who sacrificed their lives defending our Parliament and the democratic values and ethos it stands for. Their sacrifice, gallantry and commitment inspire us to fight terror and protect our revered democracy. Humble tributes!"
Union Minister Ravi Shankar Prasad said: "Today, let us remember the martyrs who sacrificed their lives defending and protecting Parliament of India from the terrorist attack."
His Cabinet colleague Prakash Javadekar posted: "Salute! Tributes to those who sacrificed their lives in 2001 Parliament attack to save the democracy."
Punjab Chief Minister Capt Amarinder Singh wrote: "I join everyone in paying tribute to the brave martyrs who lost their lives during the dastardly attack on our Parliament on this day in 2001. I salute their courage & heroism in dispelling the terror attack. Your valour will forever inspire us."
Another netizen saluted the valour of the men martyred in the attack on the "temple of democracy".She wrote: "A black day which shook the conscience of the entire nation, for some it was just another 'Lovely Day'."
Union Food Processing Minister Harsimrat Kaur Badal also posted her tributes: "Salute to the warriors who laid down their lives defending the Parliament 18 years ago. Those who breathed their last in the line of the highest duty will forever live in our hearts and in the history of our country."
Highways Minister Nitin Gadkari posted: "Ardent tributes to the martyrs and the brave who sacrificed themselves defending and protecting the #Parliament on this day today."
"Remembering our courageous soldiers, who lost their lives to save our 'Temple of Democracy' 18 years back," wrote another Twitter user.
( With inputs from IANS )