Italian military reinforcements sent to Afghanistan for the presidential election will start to return home next week, Italy's defence minister said on Tuesday.

Around 400 troops sent to boost forces for the August 20 poll will go home, following the cancellation of the run-off vote.

Two weeks ago, Italy said the reinforcements would stay in Afghanistan for the second round of voting between incumbent Hamid Karzai and challenger Abdullah Abdullah, which was planned for November 7.

Karzai was declared president for another five years on Monday after Abdullah withdrew from the run-off.

- We said the troops would stay until the end of the election process, which has now been reached, so now we are staring their gradual repatriation - Defence Minister Ignazio La Russa said, in comments reported on the political news website Affaritaliani.

With 3,250 soldiers, the Italian contingent is currently the sixth largest in the 100,000-strong international military force in Afghanistan.

Italian Prime Minister Silvio Berlusconi congratulated Karzai on his election victory and urged him to work to stabilise the troubled country.