KANDAHAR: The Taliban demanded Thursday that Afghans boycott August 20 presidential elections and instead "free their invaded country" through holy war.

In a media statement, the Islamist militia ordered its fighters to block all roads on the eve of Afghanistan's second presidential ballot and stop voters from going to polling stations.

"To achieve real independence instead of going to fake election centres, they must go to jihadi trenches, and through resistance and jihad they must free their invaded country from the invaders," the statement said.

A surge in attacks by Taliban and other militants battling the government and allied Western troops has raised concerns that insecurity will lead to poor voter turnout and throw the election's legitimacy into doubt.

The Taliban statement called for attacks on "enemy centres", understood to refer mainly to bases of Western and Afghan forces.

The Taliban, however, did not directly order strikes on voting centres, according to an e-mailed copy of the Pashtu-language statement seen by AFP.

Mujahedin (holy fighters) "must launch operations against enemy centres," said the statement signed by the Islamic Emirate of Afghanistan, which means the Taliban.

"They must prevent people from attending the elections and one day before the elections all roads and highways must be totally closed to government and civilian vehicles, and they must inform people," it said.

The Taliban, who were in government between 1996 and 2001, have previously called for a boycott of the polls, a landmark in the US and NATO-led drive to move Afghanistan towards democracy after decades of war.

Thursday's statement was released two days after the top UN official in Afghanistan, Kai Eide, urged the Taliban not to disrupt the elections, acknowledging there were "significant" security concerns.

The UN electoral assistance team noted attacks on campaign teams, cases of intimidation and the July 19 assassination of a candidate for the provincial council election to be held alongside the presidential vote.