'Our server operator told us that the Beijing Communications Administration ordered the shutdown because officials thought the issue was sensitive,' Mr Lu said.

On Monday, 68,733 signatures were collected from individuals and other websites before the shutdown went into effect.

The Beijing communications watchdog's spokesman was not available for comment yesterday.

The ministry said on Sunday that a consortium of a Chinese firm and six Japanese companies, including Kawasaki Heavy Industries, won the bullet-train bid.

The project - with an estimated contract value of 100 billion yen (HK$7.1 billion) - aims to double train speeds on five key railway lines and will cover a total length of 2,000km.

The alliance's campaign called for public hearings on the high-speed rail project and the planned Beijing-Shanghai express line, and the creation of a supervisory body under the National People's Congress to oversee the projects.

'We are appealing for more information about the status of our domestic rail projects as well as the Japanese companies taking part in the bids,' Mr Lu said.

He said the political backgrounds of the Japanese companies should be investigated to ensure they were not linked to the military.

'The railways are key to China's security. We support a rail system built by domestic companies,' Mr Lu said.

The alliance will submit petitions to the related government departments today and ask authorities to allow the website back online.

Bids for the high-speed project opened in July and all four tenders were submitted by foreign companies and consortiums led by foreign companies.

Ties between the mainland and Japan have cooled in the past few years due to issues such as visits to war shrines by Japanese leaders, a sex scandal involving Japanese tourists last year and the dispute over the Diaoyu Islands.