Neighbouring Pakistan, which on Sunday opened its Kashmir border with India to facilitate the flow of aid to quake-stricken areas, was quick to offer its condemnation within hours of the blasts.
"The attack in a crowded market place is a criminal act of terrorism," a statement issued by the Foreign Ministry in Islamabad said.
"The people and government of Pakistan are shocked at this barbaric act and express deep sympathy with the families of the victims."
Other world leaders added their condemnation of the bombings:
n New York UN Secretary-General Kofi Annan's office said in a statement he was "appalled" by the attacks.
"The secretary general is particularly shocked that this latest terrorist outrage has occurred on the eve of the major Hindu festival of Diwali," the statement said.
US Secretary of State Condoleezza Rice said the bombings were "made more heinous in that they deliberately targeted innocent civilians preparing for holiday celebrations". In a statement released in Washington she said it was "another sad reminder that terror knows no borders and respects no religion. Fighting terror is our common struggle, and we stand with the people of India as they bring to justice those responsible for these cowardly acts."
"Fighting terror is our common struggle"
Condoleezza Rice, US Secretary of State
Afghan President Hamid Karzai condemned the attacks as an "inhumane and terrorist act", adding that they "once again emphasized the expansion of the worldwide fight against terror."
British Foreign Secretary Jack Straw called the blasts "yet another example of terrorists' cynical and callous disregard for human life." He added: "On behalf of the British government, I would like to offer the people of India my support and deepest sympathy."
Australian Prime Minister John Howard called the New Delhi attacks "unforgivable". The bombings he said were "brutal and indiscriminate, deliberately targeting civilians. "It's a dreadful attack, it was in a busy area, a market area, it wasn't some kind of iconic political target," he told Nine Network Television.
"It's a dreadful attack, it was in a busy area, a market area, it wasn't some kind of iconic political target"
Australian Prime Minister John Howard
New Zealand Prime Minister Helen Clark said such cold-blooded violence aimed at innocent citizens underlined the importance of the international community working together to counter terrorism. "There can be no tolerance of such deliberate and cowardly acts of terrorism," Clark said in a statement.
In a letter to Indian Prime Minister Manmohan Singh, French Prime Minister Dominique de Villepin said "France condemns terrorism and terrorist acts with the greatest severity."
Chinese President Hu Jintao said Beijing condemned "all forms of terrorism", adding China was "willing to work together with the international community, including India, to fight terrorism and safeguard world peace and stability."
Malaysian Prime Minister Abdullah Ahmad Badawi said "I am particularly saddened by the loss of dozens of innocent lives and injury to hundreds of innocent people as a result of the attacks. Malaysia hopes the perpetrators will soon be found and brought to justice."
South African President Thabo Mbeki said his government "joins the international community in condemning these heinous acts of terrorism, particularly in a country that espouses the principles of democracy and freedom of its people."