Two explosions injured nearly 30 people in the Afghan city of Jalalabad, but it is not clear who was responsible. Also, a dozen Afghans driving a convoy of supply trucks for the U.S. military have apparently been kidnapped. The latest violence follows a plea by Afghanistan's president for more international troops to stabilize the country.

Afghan officials say the explosions in the eastern town of Jalalabad hit a crowded area. The wounded include five police officers, as well civilians shopping in the area. The bombs were reportedly hidden in crates of fruit and shattered windows of nearby homes and shops.

Last week, two women were killed and 13 others were wounded in Jalalabad when a bomb ripped through a bus carrying female election workers. In another incident, Islamic insurgents in the southern Afghan province of Zabul killed 16 people, reportedly because they had registered to vote in September's national election.

Militants linked to Afghanistan's ousted Taleban government took responsibility for those attacks. The Islamic militia has vowed to disrupt the national election in September, saying it is meant to strengthen the U.S.-backed government in Kabul.

The latest violence comes just a day after interim Afghan President Hamid Karzai pleaded for more NATO troops to provide security ahead of the elections.

Both Afghan and U.S. officials have said that anti-election violence will pick up in the days to come, but they say they are determined to deter any threat to the presidential and parliamentary election.

Speaking in Kabul Tuesday, U.S Ambassador Zalmay Khalilzad condemned attacks on election workers and said the elections will be held on time.

"Tragically, we should expect the terrorists and extremists to launch more such attacks in an effort to derail Afghanistan's historic elections," he said. "The coalition and the international community will do all that we can to prevent such violence and to hold the elections on schedule."

In another incident on Wednesday, Taleban insurgents reportedly attacked a convoy of trucks carrying food for U.S forces in the southern province of Kandahar. Twelve Afghan drivers and workers with the convoy were kidnapped.

Afghan officials, diplomats and officers in the multinational security force are trying to verify reports that an Australian journalist and her Afghan assistant and driver are missing. Neither has been heard from since Monday and there are unconfirmed reports they were captured by the Taleban.