By Krittivas Mukherjee
NEW DELHI (Reuters) - Indian Prime Minister Manmohan Singh accused Pakistan on Tuesday of acting irresponsibly, saying November's Mumbai attacks must have had support from some of its nuclear-armed neighbour's official agencies.
Pakistan rejected the accusation as unacceptable, saying India had embarked on a propaganda offensive and such charges jeopardised chances of cooperation against terrorism.
Singh's comments were the latest in almost daily government criticism of Pakistan, and a sign that New Delhi has become increasingly frustrated at what it sees as Islamabad's slowness at identifying and arresting the attack's planners.
India blames Pakistan militants for the coordinated strikes in November by 10 gunmen that killed 179 people and have revived tension between two nations that have fought three wars since 1947. Pakistan denies any involvement by state agencies.
Singh said investigations, including by intelligence agencies from some of the foreign countries whose nationals were killed in the attack, had also suggested official complicity.
"There is enough evidence to show that, given the sophistication and military precision of the attack, it must have had the support of some official agencies in Pakistan," he said.
The Pakistani government, which condemned the attacks and blamed them on "non-state actors," said it emphatically rejected Singh's accusation.
"Instead of responding positively to Pakistan's offer of cooperation and constructive proposals, India has chosen to embark on a propaganda offensive," the Foreign Ministry said, adding the approach was "fraught with grave risks."
"Vilifying Pakistan, or for that matter any of its state institutions, on this score is unwarranted and unacceptable. This is a sure way to close avenues of cooperation in combating the menace (of terrorism)," it said.
India sent evidence on Monday to Pakistan that it said linked Pakistani militants to the attacks, including data from satellite phones and what it describes as the confession of a surviving attacker.
"India has given us some material, we are examining it," Pakistan High Commissioner Shahid Malik told reporters in New Delhi. "There is no question of rejection or otherwise."
The evidence was also sent to countries whose citizens were victims of the attacks, such as the United States, as India tried to corner Pakistan diplomatically into bringing the perpetrators to justice.
Singh wants international pressure to persuade Pakistan to dismantle what New Delhi says are terrorist training camps on Pakistani territory and extradite 40 suspects.
India has said it suspects that the powerful Pakistan military spy agency ISI gave some support to the attack, and says it is frustrated by Pakistani denials.
"The more fragile a government, the more it tends to act in an irresponsible fashion," Singh earlier told a security conference. "Pakistan's responses to our various demarches on terrorist attacks is an example."
"Today even as Pakistan engages in whipping up war hysteria, our nation remains steadfastly united and if anything, the process of national consolidation is becoming stronger."
A similar attack on India's parliament in 2001 nearly sparked another war after a massive build-up of forces on their border. While New Delhi has so far focused on diplomatic initiatives, there are signs Indian officials are becoming frustrated.
Indian Foreign Secretary Shiv Shankar Menon said on Monday that it "beggars the imagination" that no Pakistani officials knew about preparations for the attack.
Adding to the diplomatic initiatives in the region, U.S. Assistant Secretary of State Richard Boucher met President Asif Ali Zardari and other Pakistan government leaders on Monday over issues that included the Mumbai attacks.
Boucher said Pakistan had done "quite a bit," detaining a "significant number" of operatives of the militant group India says was behind the attacks, and shutting down offices of a charity the United Nations says is a front for the group. But he said there had been "not much" cooperation between the two countries and urged more.
Some analysts also say India has placed too much faith in the United States and may be disappointed, given Pakistan's importance in Washington's battle against Islamist militants in neighbouring Afghanistan.
Analysts say Pakistan, if placed under pressure, can always threaten to move troops from its western border with Afghanistan, where troops are waging an unpopular, costly U.S.-supported war against Taliban militants, to its eastern border with India.
(Additional reporting by Augustine Anthony in Islamabad; Writing by Alistair Scrutton and Robert Birsel; Editing by Simon Denyer and Paul Tait)