Antonio Guterres offers to broker peace as New Delhi and Islamabad clash following deadly Kashmir attack.

The United Nations chief has called on India and Pakistan to take immediate steps to defuse tensions in the wake of the worst attack on the security forces in decades in Indian-administered Kashmir.

UN Secretary-General Antonio Guterres on Tuesday offered to broker peace as the two South Asian neighbours have been locked in a diplomatic clash following a suicide attack on February 14 in Indian-administered Kashmir that killed 42 paramilitary personnel.

Vowing a “strong response”, Indian Prime Minister Narendra Modi on Saturday gave a “free hand” to the army to punish those behind the deadly attack in Pulwama district, claimed by Pakistan-based Jaish-e-Mohammed (JeM) armed group.

Nine people, including four Indian security forces, were killed in a gun battle days after the Pulwama attack. India claimed three suspected rebels behind the attack were also among the dead.

“We are deeply concerned at the increasing tensions between the two countries,” UN spokesman Stephane Dujarric said on Tuesday.

Guterres “stresses the importance of both sides to exercise maximum restraint and take immediate steps” to de-escalate, while also offering to mediate “should both sides ask”, said Dujarric.

Maleeha Lodhi, the Pakistani envoy to the UN, said, “The situation between Pakistan and India is deteriorating.”

“We see an escalation in rhetoric from the Indian side, a spate of threatening statements by Indian leaders… The situation is very fraught,” Lodhi told Al Jazeera.

India against mediation

But India has long rejected outside offers to mediate on Kashmir issue and has maintained that the border differences should be resolved in bilateral talks. India and Pakistan, who have fought two wars over Kashmir, control parts of the Muslim-majority region.

“Never, this is not what India wants. India has always rejected mediation,” former Indian diplomat Krishan Chander Singh told Al Jazeera.

Echoing Singh’s line on mediation, Vishnu Prakash, a retired Indian diplomat, said Pakistan needs to end support to “terrorism”.

“India will take all possible measures now to make sure that this does not happen again. For this, we have to take multiple measures, including economic, political and military,” Prakash told Al Jazeera from New Delhi.

On Tuesday, India rebuffed Pakistani Prime Minister Imran Khan’s offer to investigate the latest attack as a “lame excuse”.

“We demand Pakistan to stop misleading the international community and take credible and visible action against the perpetrators of Pulwama terrorist attack and other terrorists and terror groups operating from areas under their control,” a statement by the Indian foreign ministry said.

“It is a well-known fact that Jaish-e-Mohammed and its leader Masood Azhar are based in Pakistan. These should be sufficient proof for Pakistan to take action.”

A top military commander of India has accused Pakistan’s Inter-Services Intelligence (ISI) spy agency of “controlling” the suicide attack that has caused outrage in the country, with the chorus for war dominating social media space.

‘Actionable intelligence’

India has said it has “incontrovertible evidence” of Pakistani involvement in the attack but Pakistan has accused New Delhi of “levelling allegations without evidence”.

“If you have any actionable intelligence, give it to us, I guarantee that we will take action,” Prime Minister Khan said.

The United States has thrown its support behind India and pressed Pakistan to punish those behind the attack.

“We have been in close communication with the government of India to express not only our condolences but our strong support for India as it confronts this terrorism,” US State Department deputy spokesman Robert Palladino told reporters on Tuesday.

“We urge Pakistan to fully cooperate with the investigation into the attack and to punish anyone responsible.”

US President Donald Trump has described the standoff as “horrible” and said he will put out a statement soon.

“I have watched. I have got a lot of reports on it. We will have comment (on it) at an appropriate time. It would be wonderful if they (India and Pakistan) get along,” Trump said.