The warning comes as Indonesia declared martial law in the province of Aceh and troops launched a massive offensive against separatist rebels.

Reports in the Indonesian media indicate that aircraft carrying Indonesian troops were accompanied by four UK-built Hawk jets. Last week the Indonesian News Agency reported on an inspection of troops heading to the province. It stated that 12 Scorpion tanks were among the equipment being used by the elite troops being sent to Aceh.

Amnesty International is calling on the UK government to take action if export conditions are broken and UK arms are used for internal repression or counter-insurgency.

An Amnesty International spokesperson said:

'There will be more blood on British hands, if reports are correct and UK arms are being used for repression by one of the world's most notorious armed forces in Indonesia.

'We want to know what action the UK government will take if British arms are used to commit human rights abuses in Aceh.

'This case illustrates the urgent need for stringent arms export controls. Britain and other G8 countries must stop arming repressive governments around the world.

The revelations come as Amnesty International publishes a report today, showing that the G8 countries meeting on 1 June continue to arm repressive governments around the world. At least two-thirds of all arms transfers between 1997 and 2001 came from five members of the G8: UK, US, Germany, France and Russia.

Amnesty International is calling for an international Arms Treaty, to strengthen and harmonise national controls and turn off the flow of arms to human rights abusers.

Amnesty's report is entitled A Catalogue of Failures: G8 Arms Exports and Human Rights Violations and is available online.