LONDON, Aug 18 (Reuters) - Britain warned on Saturday against travelling to Sudan's capital Khartoum due to heightened fears Western interests may be attacked.

Britain's Foreign Office said on its Web site that public services at the British embassy in Khartoum would be suspended on Sunday and Monday as a precaution.

"There is a heightened threat of terrorist attacks in Khartoum. Western interests, including British official interests, may be targeted. We advise against all but essential travel to Khartoum," the Foreign Office said.

The updated travel advice comes after Sudanese police found three weapons caches in the capital during the past week.

Police arrested eight Sudanese in connection with the stores, which mostly contained grenades and ammunition, sources at the interior ministry said.

Some local Sudanese papers initially reported that foreign Islamists had been arrested but an interior ministry source played down fears of terrorist attacks.

"All those arrested are Sudanese," the source said. "We don't consider this to be terrorist, it's just there a lot of arms getting into Khartoum these days."

The ministry source said that with the signing of a Darfur and a north-south peace deal, many former rebel armed groups had entered the capital and arms had become more prevalent. (Additional reporting by Opheera McDoom in Khartoum)