India's parliament was paralysed on Wednesday as opposition lawmakers angrily protested over the government's response to an ambush in which five soldiers were shot dead on the border with Pakistan in the disputed region of Kashmir.

The uproar, for the second day in a row, derailed the government's legislative agenda and raised question marks over whether it will be able to drive through long-pending economic reforms during the short session, which ends on Aug. 30.

Indian Defence Minister A.K. Antony told parliament on Tuesday that a group of about 20 heavily armed militants accompanied by "persons dressed in Pakistan Army uniforms" had ambushed an army patrol earlier that day near the 740-km (460-mile) Line of Control (LoC) in the Himalayan region.

It was one of the worst such attacks since the two nuclear-armed rivals signed a truce in 2003 and it cast a pall over planned talks by top Pakistani and Indian bureaucrats on disputed territorial and water issues. The talks, frozen after a border clash in January, had been expected to resume this month.

While Antony stopped short of blaming the Pakistan army for the latest attack, his ministry later issued a strongly worded statement directly accusing Pakistani soldiers of taking part in the ambush. Army officers, speaking on condition of anonymity, made similar accusations even as Pakistan strongly denied any involvement.

The defence ministry statement and army officers said the attack had been carried out by Pakistan's Border Action Team. The unit includes members of Pakistan's commando Special Services Group and irregular forces like Lashkar-e-Taiba, a Pakistan-based militant group, the army officers said.

But, in a sign that India's army and politicians were not singing from the same hymn sheet, the ministry later retracted its statement and said Antony's account represented the official record of what had happened on the border.

India is under pressure from the United States to ratchet down tensions with Pakistan to stabilise the region as foreign forces prepare to withdraw from Afghanistan.

Both U.S. Vice President Joe Biden and Secretary of State John Kerry have visited New Delhi in recent weeks to discuss Afghanistan, where India and Pakistan are vying for influence.

Opposition lawmakers chanting "Apologise! apologise!" demanded that the Indian government explain the contradiction between the two statements and accused Antony of misleading the nation about Pakistan's role in the attack.

"The defence ministry held Pakistani army fully responsible for the incident. But the defence minister gave a clean sheet to the Pakistan army and completely absolved them," Sushma Swaraj, a leader of the main opposition Bharatiya Janata Party (BJP), told parliament.

"The government must admit that the Pakistan army is responsible for this incident," she said.

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Antony stood by his statement and said as defence minister he had an obligation to be careful not to repeat information that had not been verified. But rowdy lawmakers did not accept his explanation and continued to disrupt proceedings until parliament was adjourned.

Antony's cautious statement appeared to reflect a reluctance by the Indian government, at least for now, to let the border incident damage efforts to restart the peace talks.

But with elections due by next May, there are questions over whether Prime Minister Manmohan Singh's government can pursue dialogue with Pakistan without being painted as weak by the opposition.

The BJP has repeatedly accused Singh of being soft on Pakistan and China, whose troops are also accused of border incursions.

Political heat over the killing of two Indian soldiers in a clash in Kashmir in January forced Singh to suspend the peace talks. In the intervening months, diplomats and officials from both countries have been quietly working to relaunch them.

New Pakistani Prime Minister Nawaz Sharif made improving trade with India a central plank of his election campaign and has said he wants to ease mistrust between the two countries.

Two Pakistani soldiers were wounded in an exchange of fire with Indian troops on Tuesday, officials on both sides said Wednesday.

A Pakistani military official blamed "unprovoked Indian firing" and said senior army commanders on both sides had spoken over a hotline. A senior Indian army officer in northern Kashmir said Pakistani forces had opened fire first.