One US military service member and two contractors were killed in an Islamist attack on a military base in Kenya.
Islamist militant group al-Shabab attacked the base, used by Kenyan and US forces, in the popular coastal region of Lamu on Sunday.
The US military said in a statement that two others from the Department of Defense were wounded.
"The wounded Americans are currently in stable condition and being evacuated," the US military's Africa Command said.
Witnesses to the attack reported hearing gunfire and seeing plumes of black smoke emerge from Camp Simba on Manda Island.
Gen Stephen Townsend, commander of US Africa Command, added in a statement: "Our thoughts and prayers are with the families and friends of our teammates who lost their lives today.
"As we honour their sacrifice, let's also harden our resolve. Alongside our African and international partners, we will pursue those responsible for this attack and al-Shabab, who seeks to harm Americans and US interests."
Al-Shabab is linked to al-Qaeda and is headquartered in neighbouring Somalia.
The group has carried out a spate of attacks in the region since it was formed more than a decade ago.
On 28 December, about 80 people were killed in a bombing in Somalia's capital, Mogadishu.
What happened at Camp Simba?
The Kenyan Defence Forces (KDF) said "an attempt was made to breach security at Manda Air Strip" but the attack was repulsed.
Four militants were killed, it added.
A fire caused by the attack had been extinguished and the airstrip was now safe, a KDF spokesman said.
A nearby airfield used for civilian flights had reopened, aviation officials said.
Al-Shabab said it had "successfully stormed the heavily fortified military base" before taking "effective control of a part of the base".
The group said the Kenyan military used warplanes to repel the attack.
How extensive was the damage?
The Associated Press news agency reported that two aircraft, two US helicopters and multiple vehicles were destroyed at the airstrip.
Al-Shabab said it had killed nine Kenyan soldiers and had inflicted 17 "battle casualties" on US forces.
Seven aircraft and five military vehicles had been destroyed, it added.
A journalist with Voice of Africa tweeted photos of what the militants said was a US aircraft that had been targeted.
Photos published by Al-Shabaab purportedly show militants in Camp Simba/Manda Airstrip, Lamu Kenya. pic.twitter.com/MfzeSpjNHN— Harun Maruf (@HarunMaruf) January 5, 2020
The camp has fewer than 100 US personnel, AP reported.
This was the first attack by al-Shabab on US forces in Kenya.
By BBC World Service Africa editor Will Ross
This was an audacious pre-dawn raid by al-Shabab militants.
It is not yet possible to verify al-Shabab's version of events, but there are unconfirmed reports that one of the aircraft destroyed in the attack is a US plane used for spying in the region.
The fact that this happened close to the popular tourist destination of Lamu Island is also alarming.
Since 2011, when Kenya sent troops to fight al-Shabab in Somalia, the jihadist group has carried out frequent attacks on Kenyan soil.
Almost exactly a year ago, 21 people were killed during a raid on the Dusit hotel complex in the capital Nairobi.
In June 2018, a US commando was killed in Somalia during an attack by al-Shabab.
The US has stepped up military operations against the militants since Donald Trump became president in 2017.
The US military conducted more air strikes in Somalia in 2019 than in any previous year.