Pakistan's prime minister Wednesday said the two top leaders of an Islamic militant group that India believes was behind the November 26 terrorist attacks in Mumbai were being questioned by police, reported dpa.
Meanwhile, Pakistani jet fighters, including F-16s, on Wednesday were flying over Islamabad with live ammunition as a media report said India's air defences had been put on "highest alert."
Premier Yousaf Raza Gilani said Zakiur Rehman Lakhvi and Zarar Shah were detained in a raid this week at the offices of Lashkar-e-Taiba (LeT).
According to Indian officials, the lone surviving attacker in the Mumbai siege, which left 172 people dead and more than 300 injured, had identified LeT chief Lakhvi as the mastermind.
Zarar Shah is suspected by investigators to be responsible for arranging telephone cards, internet connections and satellite phones used by the terrorists, India's The Hindu newspaper reported Wednesday.
But there has been confusion over how many leaders from outlawed militant organizations have been arrested.
Pakistan's Defence Minister Ahmad told CNN-IBN on Tuesday that the chief of another terrorist group Jaish-e-Mohammad (JeM) had also been apprehended by Pakistani security forces, but Gilani could not confirm that.
"We have yet to receive latest report on Mr Masood Azhar," he said. "As far as the other two people are concerned (Lakhvi and Shah), they are being investigated."
An unnamed JeM source said police were deployed outside Azhar's family residence in Bahawalpur, a city in eastern Punjab province. "But Maulana (Azhar) is not there, he has already left the place," he added.
Azhar is on a list of 20 fugitives India is demanding Pakistan to extradite. He was arrested by Indian authorities for alleged connection with al-Qaeda in 1994.
He was freed five years later in exchange for the release of passengers on a hijacked Indian Airlines flight. The hijackers were led by Azhar's brother, Ibrahim Athar.
After his return to Pakistan, Azhar was given a hero's welcome by Islamists, which encouraged him to set up his own group, JeM.
The recent arrests were announced by Pakistani authorities as the tensions between the two South Asian nuclear-armed countries have risen dangerously.
A report from CNN-IBN said the Indian Air Force raised its level of readiness to "Passive Air Defence." The high alert is in response to heightened perceptions of air attacks on Indian positions.
All Indian military aircraft have been armed with bombs and missiles and are ready to take off within minutes. Even the warships of the Western Naval Fleet were aggressively patrolling the Arabian Sea, the report said.
Pakistani fighter planes circled over the capital Islamabad on Wednesday morning.
"We see and hear combat aircraft flying over Islamabad but once a while. So many flights in so short time as it happened this morning is something unusual," said local resident Muhammad Iqbal.
A spokesman for Pakistan Air Force (PAF) told Deutsche Presse-Agentur dpa they had no means to confirm the reports about alert status of the Indian Air Force, but said: "PAF is ready to defend the country."
He confirmed that the planes were making "armed sorties" over Islamabad, but he insisted it was a regular exercise. Asked if in every regular exercise, the jet fighters carry live ammunition, he declined to reply.
According to the DawnNews channel, Pakistan Navy also said it was alert to the movements of Indian vessels.
"Pakistani armed forces are highly professional and among the best militaries in the world. Therefore, we need not to have any kind of worries," Gilani told reporters in Multan when asked to comment on the reports about air force alerts in India.
The report on CNN-IBN said the Indian alert was still defensive, and had been sounded in view of intelligence reports of possible air strikes at Indian installations from across the border or an aerial attack by terrorist groups based in Pakistan.
Under the alert, leaves of all key personnel in the Western and South-Western Air Commands, which face Pakistan, have been cancelled. But there was still no mobilization of troops on the border and the Indian Army is not on the highest alert level, the report said.