Speaking at the party headquarters in Thiruvananthapuram, she said: "Incidents of communal violence, especially in some states of the north like Uttar Pradesh, Maharashtra and some other states have increased in the 11 weeks since the new government came to power.
"And it is something which is of great concern and worry to all of us.
"During the UPA government, UPA I and UPA II, there were hardly any such incidents. But in a very short span, we have had nothing less than 600 communal violence incidents in UP and perhaps as many in Maharashtra. This of course makes us wonder and makes us think why suddenly after the BJP has come to power all these communal incidents...," she said.
"...and what we believe and what is pretty clear in many instances is that these incidents are deliberately created to divide our society along religious lines," Gandhi added.
Her attack on the Modi government came after her son and party vice president Rahul Gandhi slammed the Centre on the issue.
He held an unprecedented noisy protest and also trooped to the Lok Sabha Speaker's podium Aug 6, demanding a debate on rising communal violence in Uttar Pradesh.
Modi took a dig at Rahul Gandhi in his speech at the party national council meet, saying "those who have suffered a massive defeat in the elections are still not able to desist from engaging in old vote bank politics".
He had also said: "The BJP never accepts incidents (of violence) which are taking place in the country. Peace, unity and harmony are the pre-requisites for progress and there will be no compromise on this."
Rahul Gandhi had said the violence in Uttar Pradesh was "artificially and deliberately engineered".
In New Delhi, Minister of State in Prime Minister's Office Jitendra Singh told reporters outside parliament house: "I do not think it is necessary for us to comment on these off-the-cuff remarks made by anybody. What is happening is known to everybody, it is very evident.
"We live in an evidence-based era of arguments. So, I do not think we should attach much importance to what somebody is saying," he said.
He said the prime minister and his government's stand on all these issues was more than clear.
Shiv Sena spokesperson Sanjay Raut said: "The Modi government is not responsible for whatever is happening in Uttar Pradesh... Sonia Gandhi should understand as to who is ruling there and what is the situation there."
However, Sitaram Yechury of the Communist Party of India-Marxist endorsed Sonia Gandhi's views.
"That is what the home ministry statistics indicate (that incidents of communal tension had increased) in 2013 and now in the second quarter they are much more.
"They are rising in direct proportion to the by-elections that are happening. And in the 12 constituencies where the by-elections are due, you find communal tensions rising very sharply," he said.
Sonia Gandhi further criticised the Modi government for its attitude towards the happenings at Gaza.
"In the Lok Sabha, we were unable to initiate a discussion, but in the Rajya Sabha we were able to take up the issue for discussion. We have always expressed our solidarity with the Palestinians. At the moment, the guns there have fallen silent," she said.