Japanese Prime Minister Yukio Hatoyama has announced his resignation after just eight months in office.

He was forced out after breaking an election pledge to move an unpopular US military base away from the southern island of Okinawa.

The move comes as his Democratic Party of Japan (DJP) struggles to revive its chances in an election due in July.

The centre-left DPJ's election landslide last year ended half a century of conservative rule in Japan.

But wrangling over the base distracted attention from their broader aims - pursuing a more equal alliance with the US, a bigger welfare state, and to seize control of policy-making from the bureaucracy, the BBC reported.

Hatoyama, 63, was Japan's fourth prime minister in four years.

Until Tuesday night, Hatoyama had insisted he would stay on while intermittently holding talks with key members of his Democratic Party of Japan.

But he announced his resignation at a special meeting of DJP lawmakers on Wednesday.

He said he had asked Ichiro Ozawa, the party's secretary general, known as the "Shadow Shogun" for his power behind the scenes, to go too.