Japanese PM in coma

Keizo Obuchi at a G8 meeting in Tokyo on Saturday

Japan's Prime Minister Keizo Obuchi has slipped into a coma after suffering a stroke at the weekend.

Now on a life-support machine, Mr Obuchi was at first reported to be suffering from exhaustion when taken to hospital on Saturday.

Chief Cabinet Secretary Mikio Aoki, who has taken over as acting head of government, said on Monday that Mr Obuchi's condition was extremely severe and that his resignation was unavoidable.

Mikio Aoki: Caretaker prime minister

Mr Aoki said he would decide whether to dissolve the cabinet, so that a new leader could be installed, once Mr Obuchi's prognosis became more clear.

The acting prime minister had previously said that he had held a conversation with the ailing prime minister on Sunday.

"Obuchi said we could not have any delay in our measures to cope with the volcanic eruption so he appointed me as acting prime minister," Mr Aoki said.

At that stage, Mr Obuchi was said to be "calm" and "speaking clearly".

Prolonged hospital stay

Reports from Tokyo say the prime minister's resignation is expected to come in the next day or two.

Local newspapers are already speculating on who might succeed Mr Obuchi, as Mr Aoki is seen as only a temporary replacement.

Two politicians named were Foreign Minister Yohei Kono and the secretary-general of Mr Obuchi's ruling Liberal Democratic Party (LDP), Yoshiro Mori.

BBC Tokyo correspondent Juliet Hindell says the process of finding a new leader should be a smooth one, as other political parties are not rocking the boat at the moment.

Under pressure

Mr Obuchi, 62, suffers from a heart condition for which he has a pacemaker. He was taken to Juntendo Hospital at 0100 local time on Sunday (1600 GMT Saturday).

When he became prime minister in July 1998, questions were raised about the state of his health, but there have been no reported problems since he took office.

Earlier, NHK television reported that Mr Obuchi had become severely tired from handling the government's response to the volcano on the island of Hokkaido.

Mr Obuchi has worked long hours dealing with the volcanic eruption

Mount Usu exploded into life on Wednesday for the first time in more than 20 years, forcing thousands of people to take shelter.

Over the past few days, the prime minister has also had to deal with the break-up of his governing coalition.

The prime minister governs with a large majority in parliament because the LDP is allied with the Buddhist-backed Komeito Party and the smallest member, the Liberal Party.

But Mr Obuchi said on Saturday that the three-party coalition would break up after he rejected demands from Liberal Party leader Ichiro Ozawa for a series of reforms.

The break-up led to opposition demands over the weekend for a snap election.

The Japanese Government is also preparing to host the G8 leaders' summit in July.