A suicide car bomber blew himself up Tuesday in Lashkar Gah, the capital of Afghanistan's volatile southern Helmand province, killing at least two people and wounding 26 others, including 10 police officers.

The provincial government spokesman Dauod Ahmadi said the explosion occurred on a busy street outside a police station.

The Taliban has claimed responsibility for the attack.

Lashkar Gah was one of seven areas where control of security passed from foreign to Afghan forces in July, as part of the first wave of a transitional process that is due to have all foreign combat forces leave Afghanistan by the end of 2014.

In western Herat province, a passenger bus returning from a wedding hit a roadside bomb, killing 16 people, including 11 children.

The international coalition joined Afghan President Hamid Karzai in condemning the blast. In a statement Tuesday, the NATO-led forces said only enemies of peace and stability could take such actions that kill innocent women and children.

Hundreds of demonstrators gathered in Kabul Tuesday to call for an international investigation into last week's assassination of former president Burhanuddin Rabbani, who was leading the nation's peace negotiations with the Taliban.

The protest was led by former intelligence chief Amrullah Saleh, who stepped down last year after opposing the government's efforts to hold talks with the Taliban.

Many of the demonstrators held signs saying, “Death to the Taliban” and “Death to Pakistan.”

Mr. Rabbani was killed a week ago at his home in Kabul by a suicide bomber pretending to deliver a “message of peace” from Taliban leaders.

Some Afghan officials have hinted that a recent series of targeted assassinations of Afghan officials may have been coordinated in part by Pakistan, a charge Islamabad denies.