Mogadishu - A US military plane landed in Somalia's capital on Tuesday with medical and humanitarian aid supplies after Saturday's massive truck bomb that killed more than 300 people.A spokesperson for the US Africa Command told The Associated Press that the charge d'affaires of the US Mission to Somalia "declared that this disaster meets the criteria to warrant immediate US government assistance" because of the widespread damage.Another nearly 400 people were injured in the deadliest attack in Somalia's history and one of the world's worst attacks in years. Scores remain missing and the death toll could still rise, said officials.Funerals have continued and dozens of critically injured have been airlifted to Turkey for treatment. The international aid response to the attack was growing; a medical team from Djibouti arrived on Monday to evacuate the wounded. Kenya will evacuate 31 injured Somalis from Mogadishu for specialised treatment in Nairobi and send 11 tons of medicine and supplies to Somalia, Kenya announced on Tuesday.Somalia's government has blamed the attack on the al-Shabaab extremist group, which has not commented.But analysts said there is little doubt that Africa's deadliest Islamic extremist group carried out the bombing. "No other group in Somalia has the capacity to put together a bomb of this size, in this nature," said Matt Bryden, a security consultant on the Horn of Africa.As the death toll rose to 302, overwhelmed hospitals in Mogadishu were struggling to treat badly wounded victims. Nearly 70 people are missing, based on accounts from relatives, said police Captain Mohamed Hussein.Al-Shabaab has waged war in Somalia for more than a decade, often targeting high-profile areas of the capital. Earlier this year, it vowed to step up attacks after both the Trump administration and Somalia's recently elected Somali-American president, Mohamed Abdullahi Mohamed, announced new military efforts against the group.The US military has stepped up drone strikes and other efforts this year against al-Shabaab, which is also fighting the Somali military and 22 000 African Union forces in the country.Saturday's explosion shattered hopes of recovery in an impoverished country left fragile by decades of conflict, and it again raised doubts over the government's ability to secure the seaside city of more than 2 million people.International condemnation has poured in, with the United States calling the attack "cowardly" and the United Nations special envoy to Somalia calling it "revolting".Michael Keating said the UN and African Union were supporting the Somali government's response with "logistical support, medical supplies and expertise".