Alarm and concern began to spread like wildfire in Nepal after former prime minister Girija Prasad Koirala, the architect of the peace negotiations that ended a decade of Maoist insurgency, slipped into a coma Saturday after suffering from respiratory problems for nearly a fortnight.

A private TV channel and a leading media house said in separate reports, quoting unnamed family and party sources, that the octogenarian leader who fell unconscious early morning, passed away soon after noon.

However, Koirala's Nepali Congress party declined to comment on the reports, saying it would issue an official statement only after an emergency meeting of its leaders.

Armed police forces were put on alert after the 85-year-old, who heads the Nepali Congress, the largest party in Nepal's ruling alliance, lapsed into unconscious with his team of physicians failing to revive him.

Koirala, hailed by former US president and Nobel Peace Laurate Jimmy Carter as his hero for having brought the Maoist guerrillas to mainstream politics, had been discharged from the Shahid Gangalal Memorial Heart Hospital Wednesday, where he had been admitted after suffering from a low haemoglobin count due to chronic lung problems.

Once a chain smoker, Koirala had asked to be discharged from hospital and be taken to the residence of his daughter, Deputy Prime Minister Sujata Koirala, rejecting the recommendation by doctors to be flown abroad for treatment.

In the recent past, he had been admitted to hospitals in New Delhi, Thailand and Singapore.

Koirala, who began his career as a trade union leader from a jute mill in Biratnagar town in southeastern Nepal, was exiled to India for taking part in a pro-democracy movement opposing the absolute rule of Nepal's hereditary Rana prime ministers.

He was also jailed by king Mahendra for opposing the absolute rule of the Shah dynasty of kings.

Hailing from a family that saw three brothers become prime ministers, Koirala himself ruled Nepal as premier for five times.

Though his leadership was marred by feuds within the party that saw it split and stoked the Maoist insurgency due to rising corruption, Koirala is respected for his unflagging opposition to King Gyanedra's attempt to rule Nepal with the help of the army.

He is also regarded as an unwavering friend of India though his exile in India became controversial after his admission that he had been involved in counterfeiting Indian currency to raise funds for the pro-democracy struggle.

He was also involved in a plan by the Nepali Congress to hijack an aircraft from Nepal to India, allegedly carrying a cargo of money.

The government of Nepal had decided to nominate Koirala for the Nobel Peace Prize for his role in signing a peace pact between the Maoists and the major parties.

The Nepali Congress said it would issue a statement on Koirala's condition only after an emergency meeting of the party.

'The central committee of the Nepali Congress is meeting at Sujata Koirala's residence at 1pm,' NC deputy chief Gopal Man Shrestha told IANS.

'Koirala's condition is critical. But the doctors are doing their best to revive him.'

President Ram Baran Yadav, Koirala's former protege, and Prime Minister Madhav Kumar Nepal headed towards Koirala's residence.

Maoist chief Pushpa Kamal Dahal Prachanda, whose party served a shock defeat to Koirala's Nepali Congress in 2008 and became the biggest challenger to Koirala's hold on national politics, also rushed to Koirala's residence.

However, the ailing leader, lying in a stupor, failed to respond to his greetings.

The passing away of the octogenarian leader will deal a grave blow to Nepal's peace process that is to culminate in a new constitution on May.

In Koirala's absence, there is no other leader of his stature who can hold the bickering parties together.

The Nepali Congress also faces an internal war for succession. Koirala, who kept an iron grip on the party, had indicated he wanted his mantle to fall on his daughter.

However, her bid to lead the party is likely to be opposed by former premier Sher Bahadur Deuba, who split the Nepali Congress in the past after a leadership tussle.