TOKYO - THE suspected murder of a former vice health minister and the stabbing of the wife of another, both with careers tied to Japan's ailing pension system, prompted Japanese police to tighten security for officials on Wednesday.

The attacks follow a series of scandals involving pensions and health care for Japan's rapidly ageing population, including the mishandling of millions of pension records.

The introduction of a medical insurance scheme that forced some elderly citizens to pay more also angered the public.

A former vice health minister and his wife were found dead at their home on Tuesday from what appeared to be multiple stab wounds, police said.

The wife of another former vice health minister was later stabbed at her home by a man disguising himself as a delivery man. Her wounds were not fatal.

'I don't know if the two incidents are linked, but it is heartbreaking,' Prime Minister Taro Aso told reporters.

'I am praying for the souls of those who were killed and the recovery of the (official's wife) who was wounded.'

The health ministry late on Tuesday alerted its top officials and gave the National Police Agency names and addresses of former senior officials so it could step up security around their homes.

BLOODY FOOTPRINTS

Security was also tightened at the ministry, where metal-detecting wands were being used to check visitors.

'It is not yet clear if the two incidents are linked, but police are investigating this with the possibility that these were related terrorist attacks,' top government spokesman Takeo Kawamura told a news conference.

Kyodo news agency said police were checking to see whether bloody footprints at the sites of the two attacks matched.

Japanese policy makers are struggling to revamp strained pension and social welfare systems and find ways to fund the growing costs of one of the world's fastest ageing populations.

Two out of every five people are forecast to be aged 65 or over by 2050, twice the current proportion.

A series of scandals involving mishandled and doctored pensions records has added to public outrage and anxiety.

'We know there is deep angst. Every poll tells you the overwhelming worry is about retirement and the messed up pension system,' said Ms Jesper Koll, CEO of investment consultancy Tantallon Research Japan.

The pension records scandal contributed to the ruling party's loss in an upper house election last year and helped topple Prime Minister Taro Aso's two predecessors from office.

Both resigned after their support rates sank sharply. -- REUTERS