UPDATE 2-Islamic State claims attack that killed 28 soldiers in Niger

(Adds claim of responsibility from Islamic State, background)
NIAMEY, May 16 (Reuters) - Islamic State's West African
branch on Thursday claimed responsibility for an ambush that
killed 28 soldiers this week in Niger, as the militant groups
seek to establish roots in the impoverished Sahel region.
Tuesday's ambush occurred near the town of Tongo Tongo,
where fighters from an Islamic State affiliate killed four U.S.
special forces and four Nigerien soldiers in an ambush in
October 2017.
Government soldiers were pursuing gunmen who had earlier
attacked a high security prison, when one of their vehicles rode
over a mine and they came under fire, government spokesman
Abdourahamane Zakaria told Reuters.
The claim of responsibility was translated into English and
published on the SITE Intelligence website.
Islamist militants loyal to Adnan Abu Waleed al-Sahrawi, the
leader of Islamic State in the Greater Sahara, operate along
Mali's border with Burkina Faso and Niger, in the vicinity of
Tuesday's attack.
The other regional group claiming allegiance to Islamic
State -- IS West Africa Province or ISWAP -- is based more than
1,000 miles away, in southeast Niger.
The attack, one of the deadliest against the military in
Niger's west in recent years, marks a major setback for military
operations trying to restore order in a region plagued by
jihadist groups and allied criminal gangs.
Despite years of heavy deployments of French, U.S. and U.N.
forces, Africa's Sahel region remains a tinderbox of Islamist
fighters, ethnic militias and criminal smuggling rackets.
The border areas where Niger, Burkina Faso and Mali meet are
especially dangerous and violence is worsening across the
region. Gunmen suspected to be Islamists killed at least 10 in
apparently sectarian attacks on churches in neighbouring Burkina
Faso this week.