Mogadishu - The US military said on Friday it carried out a drone strike this week against al-Shabaab in Somalia, shortly after the extremist group was blamed for the country's deadliest attack, while thousands of anguished Somalis gathered at the site of the truck bombing to pray."This pain will last for years," said a sheikh leading the prayers, with long lines of mourners standing in front of flattened or tangled buildings. More than 300 people were killed and nearly 400 wounded in Saturday's attack, with scores missing.The US drone strike occurred on Monday about 56km southwest of the capital, Mogadishu, the US Africa Command told The Associated Press. It said it was still assessing the results.Al-Shabaab has not commented on the bombing, which Somali intelligence officials say was meant to target Mogadishu's heavily fortified international airport. Several countries have embassies thereThe US has stepped up its military involvement in the Horn of Africa nation since President Donald Trump approved expanded military operations against the group early this year. The US has carried out at least 19 drone strikes in Somalia since January, according to The Bureau of Investigative Journalism, which tracks US drone strikes in a number of countries.Earlier this week, a Pentagon spokesperson said the United States has about 400 troops in Somalia and "we're not going to speculate" about sending more.In April, the US announced it was sending dozens of regular troops to Somalia in the largest such deployment to the country in roughly two decades. The US said it was for logistics training of Somalia's army. At the time, the US said about 40 troops were taking part.Weeks later, a US service member was killed during an operation against al-Shabaab.