The fugitive Taliban leader Mullah Mohammad Omar has urged his followers to step up their suicide attacks on foreign and Afghan troops and remain united, according to a Taliban commander.

Violence has surged in Afghanistan in recent weeks after a winter lull, following last year's bloodiest period since 2001.

Taliban commander Mullah Hayatullah Khan told reporters late on Friday by satellite phone from an undisclosed location that Omar had contacted senior and regional commanders and congratulated them for carrying out "successful" attacks in recent weeks.

He would not give details as to how and when Omar contacted the commanders.

"Taliban mujahideen (holy warriors), through unity in their ranks, should continue and increase their guerrilla and suicide attacks on occupation forces and the infidels will soon run away," Khan quoted Omar as saying.

"Mullah Omar has ordered us to liberate our country; we should step up attacks on occupation forces and their puppet Afghans," he said.

The Taliban often refer to Western-backed President Hamid Karzai and his associates as puppets.

Omar, who has a $10 million government bounty on his head, told his fighters to try not to harm innocent civilians during their offensives, Khan added.

More than 1000 civilians have been killed in the country in the past year.

The head of Nato's operations in Afghanistan said on Thursday that he expected to see more suicide attacks and roadside bombings from the Taliban but saw this as a sign of desperation because they lacked military muscle.

Omar's whereabouts are not known, although Afghanistan's government insists he lives and operates in Pakistan, the former key supporter of the Taliban until the September 11 attacks on the United States in 2001.

However, Islamabad denies this and the Taliban say he lives in Afghanistan and co-ordinates attacks from there.

The Taliban and their Islamic allies, such as the wider al-Qaeda network, are largely active in southern and eastern areas of Afghanistan close to the border with Pakistan. The Taliban have been copying suicide attacks and kidnapping tactics from militants in Iraq.

On Friday they threatened to kill two French aid workers captured early this month if Taliban demands were not met within one week.

The Islamic group has told France to withdraw its 1100-strong force from Afghanistan and wants the release of Taliban prisoners held by the Afghan government.

The Afghan president, Hamid Karzai, has vowed his government will do all it can to free the two French nationals. However, he has ruled out any ransom deal for foreign or Afghan hostages after he was criticised for freeing five Taliban prisoners last month in return for the release of an Italian journalist.

Yesterday, small blasts occurred in two cities of northern Afghanistan, witnesses said. The explosions, one outside a government building and one outside a shop, caused slight damage but no injuries.

8:25pm Saturday 21st April 2007