MOGADISHU, Somalia (AP) — The Latest on deadliest attack in Somalia's history (all times local):

7:20 p.m.

Somalia's president is urging the long-fractured nation to "unite as politicians and public" to fight the extremist group al-Shabab after the country's deadliest attack.

Mohamed Abdullahi Mohamed spoke to thousands who marched through Mogadishu and rallied at a city stadium.

Saturday's massive truck bombing killed more than 300 people and wounded close to 400. Scores are said to remain missing.

Mohamed says they were "unfairly massacred." He announced a new task force "tasked with the protection of the people, and I shall be the first one to enlist and head to the front lines. We have to stand firm in defending our country."

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6:45 p.m.

Thousands of protesters have gathered at a stadium in Somalia's capital in a show of defiance after the country's deadliest attack killed more than 300.

The protesters chanted slogans against the extremist group al-Shabab, which Somalia's government blames for the attack.

Mogadishu's mayor urged the crowd to "liberate our country from al-Shabab, so that such tragedies won't happen again."

Nearly 400 people were wounded. Scores remain missing.

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2:45 p.m.

Officials in Somalia say two people have been arrested in connection with Saturday's massive truck bombing that killed more than 300.

A Somali intelligence official investigating the attack tells The Associated Press that a well-known man who vouched for the truck and persuaded soldiers to allow it into Mogadishu is now in jail. The official spoke on condition of anonymity because he was not authorized to speak to reporters.

The official says the truck bomber had an accomplice driving a minivan packed with explosives that took another route but was stopped at a checkpoint near Mogadishu's airport.

A senior Somali police officer, Capt. Mohamed Hussein, says that driver is now being held in a local prison.

— Abdi Guled in Mogadishu.

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2:15 p.m.

A senior Somali police official says at least three people, including a pregnant woman, are injured after security forces opened fire while trying to disperse protesters marching toward the site of Saturday's huge truck bombing in Mogadishu.

Capt. Mohammed Hussein says both Somali police and African Union soldiers were at the scene and opened fire.

Thousands of people are marching through Mogadishu in a show of unity and defiance after the bombing killed more than 300 people and wounded nearly 400. Scores remain missing.

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1 p.m.

Pope Francis has deplored the Somalia bombing that killed more than 300 people and wounded nearly 400 others.

At the end of his Wednesday public audience in St. Peter's Square, Francis said "this terrorist act merits the strongest laments" especially since it struck an already suffering population.

He prayed for the dead and wounded in Saturday's truck bombing in Mogadishu. Francis also appealed for the "conversion of the violent ones" and encouraged work for peace.

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12:45 p.m.

Somali police say African Union soldiers have fired at angry protesters marching toward the site of the country's deadliest attack.

Officer Ahmed Ali says the troops were responding after some protesters threw stones at them.

Thousands of people are marching through Mogadishu in a show of unity and defiance after Saturday's truck bombing killed more than 300 people and wounded nearly 400. Scores remain missing.

Somalia's government has blamed the attack on the al-Shabab extremist group, which often targets Mogadishu but has not commented.

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12:30 p.m.

Thousands of people have taken to the streets of Somalia's capital in a show of defiance after the country's deadliest attack.

Wearing red headbands, the crowd of mostly young men and women is marching through Mogadishu amid tight security.

"May Allah punish those who massacred our people," said university student Mohamed Salad.

The crowd marched toward the site of Saturday's truck bombing, which killed more than 300 people and wounded nearly 400. Scores remain missing.

"You can kill us, but not our spirit and desire for peace," said high school teacher Zainab Muse.

Somalia's government has blamed the attack on the al-Shabab extremist group, which often targets Mogadishu but has not commented.

Mayor Thabit Abdi called for Wednesday's march, saying "we must liberate this city which is awash with graves."