Armed extremists stormed a hotel in the Somali capital where they killed 20 people on the spot in addition to many injured, and Somali forces are still trying to end the siege of the hotel after about 24 hours since the start of the attack. Gunfire could be heard on Saturday evening as security forces tried to contain the last militants believed to be hiding on the upper floor of the hotel.

While the extremist Islamic group Al-Shabaab, which has ties to Al-Qaeda, claimed responsibility for the attack, in its latest repeated attempts to strike places visited by government officials, the attack on the hotel is the first major terrorist incident in Mogadishu since the new Somali leader Hassan Sheikh Mohamud took power in May.

The U.S. Embassy in Somalia tweeted that it "strongly condemns" the attack on the "Hyatt" hotel, stating, "We offer our heartfelt condolences to the families of the dead, wish a full recovery to the injured, and pledge to continue supporting Somalia in holding the killers accountable."

There was no immediate news about the identity of the victims, but many of them are believed to be civilians.

Meanwhile, Mohamed Abdirahman, director of the City Hospital in Mogadishu, told the Associated Press that 40 people were admitted there injured in the attack, saying that while nine were sent home after treatment, five are in critical condition in intensive care.

Witness Abdullah Hussein said over the phone, "We were having tea near the hotel lobby when we heard the first explosion followed by gunfire. I immediately rushed towards the hotel's ground floor rooms and closed the door; after that, the militants directly went up to the upper floor and started firing. At that time, I was inside the room until security forces arrived and rescued me," and he said he was on his way to a safe place when he saw "several bodies lying on the ground outside the hotel reception."

The organization has seized more territory in recent years, exploiting divisions among Somali security personnel, as well as disputes between the government seat in Mogadishu and regional states, and it still poses the biggest threat to political stability in the troubled Horn of Africa nation.

After being forced to withdraw from Mogadishu in 2011, Al-Shabaab began slowly returning from rural areas it retreated to, defying the presence of African Union peacekeeping forces as well as U.S. drone strikes targeting its fighters. The militants attacked an African Union peacekeeping military base outside Mogadishu in early May, killing many Burundian troops. The attack came just days before the presidential elections that brought Mohamud back to power after five years of his dismissal.