(Recasts with latest fresh blast)

By Kamal Sadat

KHOST, Afghanistan, April 22 (Reuters) - At least 11 people were killed and 10 wounded in a suicide blast and two separate bomb explosions in Afghanistan on Sunday, officials said.

The first blast occurred in a mobile telephone shop in a crowded produce market in the heart of the southeastern town of Khost, the scene of a series of Taliban attacks in recent weeks.

An hour later a suicide bomber blew himself up after being chased by police, just metres away from the previous explosion.

A roadside bomb exploded later in the day in the eastern province of Laghman, killing four security officials travelling in a car, police said.

Violence has been rising in Afghanistan following a winter lull, after last year witnessed the bloodiest fighting since the Taliban were ousted in 2001.

The Taliban's fugitive leader Mullah Mohammad Omar recently urged followers to step up suicide raids, a Taliban commander told Reuters on Friday, and the commander of NATO forces in the country has also said he expects to see more attacks.

Sunday's suicide explosion killed three civilians, said Wazir Badshah, a senior provincial police officer.

"Police had spotted the suicide bomber who began to run away and, before being caught, blew himself up, killing three civilians and wounding several people, including police," he told reporters close to the scene.

Shopkeepers had quickly shut down their businesses after the first blast when police warned them another bomb could explode.

A doctor at a local hospital said seven men were killed and many more wounded in the blasts.

No one claimed responsibility for the bombs, but shopkeepers suspected the Taliban and said the target may have been the mobile phone shop, where residents regularly download music into their phones.

The Taliban have targeted music shops in the past as part of their harsh interpretation of Islam. Music, film and videos were banned under their 1996-2001 rule of Afghanistan.

The radical insurgent force and their Islamic allies, including the al Qaeda network, are largely active in southern and eastern areas close to the border with Pakistan.

The group has vowed to drive out foreign troops from Afghanistan and topple the elected and Western-backed government of President Hamid Karzai.

Close to 4,000 people were killed last year. Several hundred, including about 30 Western troops, have died so far this year, regarded as a critical period for all concerned.

The new NATO commander told journalists in Kabul on Thursday he saw the expected increase in roadside bomb attacks and suicide raids as an act of desperation on the Taliban's part and a sign they lacked military might.

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