While "strongly" condemning the attack, Yechury asked why no precautionary measures were taken based on the intelligence inputs.
"This is very unfortunate. We strongly condemn the attack. But despite very good intelligence inputs, why were precautionary measures not taken," Yechury asked, referring to Monday's attack that left seven pilgrims dead.
"The government has to explain why this happened despite intelligence reports. Why no action was taken (on intelligence reports)?"
Attacking the BJP, Yechury said the last time such an attack occurred was in 2000 when there was a BJP-led government at the Centre.
He added that the government must do everything to identify those responsible for the carnage and bring them to book.
"Future security must be beefed up so that such things do not recur," he said.