MUMBAI, India (AP) – India suspects two senior leaders of a banned Pakistani militant group orchestrated the deadly Mumbai attacks, officials said Thursday, as Pakistan’s president vowed “strong action” against any elements in his country involved in the siege.

President Asif Ali Zardari made the pledge during a meeting with Secretary of State Condoleezza Rice in the Pakistani capital of Islamabad. Rice said she is satisfied with Pakistan’s commitment to fight terrorism and its readiness to pursue any lead in the attacks that left 171 people dead in India’s financial capital.

Evidence collected in probes so far has pointed to two members of outlawed Pakistani group Lashkar-e-Taiba as masterminds in the attacks, according to two Indian government officials familiar with the matter. The men, Zaki-ur-Rehman Lakhvi and Yusuf Muzammil, are believed to be in Pakistan, the officials said. Lakhvi was identified as the group’s operations chief and Muzammil as its operations chief in Kashmir and other parts of India. The lone surviving gunman in the assault told police Lakhvi recruited him for the operation, and the assailants called Muzammil on a satellite phone after hijacking an

Indian vessel en route to Mumbai. During the attacks, the gunmen used mobile phones taken from hotel guests to place calls to the Pakistani city of Lahore.

The Indian officials spoke on condition of anonymity because they weren’t authorized to talk publicly discuss the details.

The revelations added to the growing evidence linking the attacks to Pakistani-based militants, and came as Rice met with leaders in Islamabad Thursday after visiting India’s capital, part of a U.S. effort to pressure Pakistan to share more intelligence and pursue terrorist cells believe rooted in the country.

“I have found a Pakistani government that is focused on the threat and understands its responsibilities to respond to terrorism and extremism,” she said after meeting Zardari.

In the meeting, Zardari “reiterated that the government will not only assist in (the) investigation but also take strong action against any Pakistani elements found involved in the attack,” his office said in a statement. He said Pakistan was “determined to ensure that its territory is not used for any act of terrorism,” the statement said.

U.S. Joint Chiefs of Staff Chairman Mike Mullen, who was pushing the same message as Rice in Pakistan on Wednesday, was to meet with officials in India during his trip.

Last week’s attacks were carried out by 10 suspected Muslim militants against upscale hotels, a restaurant and other sites across Mumbai.

Indian airports, meanwhile, were put on high alert after the government received warnings of possible airborne attacks. No details about the threat were released. “This is a warning which we have received. We are prepared as usual,” India’s air force chief, Fali Homi Major, told reporters Thursday.

Government security forces have come under intense criticism they missed warnings and bungled their response to the Nov. 26-29 attacks.

On Thursday, police said an unexploded hand grenade was found outside a hospital that was the scene of an attack during last week’s siege on the city. The grenade may have been left by the gunmen, but an investigation has not yet been completed, said Senior Police Inspector Shashi Pal. The discovery came after police detected two bombs at Mumbai’s main train station Wednesday, nearly a week after they were left there by the attackers.

It was not clear why the bags at the station were not examined earlier. The station, which serves hundreds of thousands of commuters, was declared safe and reopened hours after the attack.

Fallout from the attacks widened Thursday as the chief minister of Maharashtra state, where Mumbai is located, stepped down. The country’s top law enforcement official resigned last week. “I regret that we could not have saved more lives, that regret will remain with me,” the minister, Vilasrao Deshmukh, told reporters.

With public anger over the attacks rising by the day, Foreign Minister Pranab Mukherjee on Wednesday adopted a more strident tone against India’s longtime rival, saying there’s no doubt the assailants were Pakistani and their handlers in Pakistan.

Many Indians wanted more than just harsh words. “Pakistan has been attacking my country for a long time,” protester Rajat Sehgal said at a candlelight gathering in Mumbai, one of a series of rallies across India. “If it means me going to war, I don’t mind.”

Much of the evidence tying Pakistanis to the attacks comes from the interrogation of the surviving gunman, who told police that he and the other nine attackers had trained for months in camps in Pakistan operated by the banned militant group Lashkar-e-Taiba.

Ajmal Amir Kasab, 21, told investigators his recruiters promised to pay his family from an impoverished village Pakistan’s Punjab region $1,250 when he became a martyr. Kasab’s father is a street vendor and his mother a housewife. His brothers are farmhands and laborers and before joining the militant groups, Kasah worked as a laborer with his brother in Lahore, according to officials close to the investigation.