Driven from its self-styled caliphate in Iraq and Syria, Islamic State is down but not out.
Where once they confronted armies, the extremist Islamist group's adherents have now staged hit-and-run raids and suicide attacks. In some cases, the group has claimed responsibility for atrocities, including the bombings of churches and hotels in Sri Lanka that killed more than 350 people.
Its involvement is not always proven, but even if the link is ideological rather than operational, Islamic State still poses a security threat in many countries.
After its defeat by U.S.-backed forces, IS has reverted to the guerrilla tactics it was once known for. Sleeper cells have regrouped in Diyala, Salaheddin, Anbar, Kirkuk and Nineveh provinces, where they carry out frequent attacks, including kidnappings and bombings aimed at undermining the Baghdad government.
In February, two people were killed and 24 wounded when a car bomb went off in Mosul, once the group's Iraqi capital.
The Pentagon said in January that IS was regenerating faster in Iraq than in Syria. Analysts estimate that 2,000 active combatants now operate in Iraq.
After serious military setbacks, IS slipped into the shadows, staging suicide bombings and ambushes.
IS has carried out bomb attacks in towns and cities of northeast Syria in recent months, including some targeting U.S. forces.
Syrian Kurdish forces, which control the region and crushed the jihadists with U.S. help, have sounded the alarm about the group's new tactics.
They believe sleeper cells have mushroomed across eastern Syria and expect guerrilla attacks to escalate. They also warn of the risk posed by holding thousands of militants in prison camps.
IS fighters still hold some ground in Syria's remote central desert, where they have staged attacks in recent days.
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Nigerian group Boko Haram has carried out attacks in the northeast since 2009 in pursuit of a caliphate. It has killed 30,000 people and forced 2 million to flee their homes.
The group split in 2016 and one faction pledged allegiance to IS. Islamic State's West Africa Province (ISWAP) has focused on attacking military bases in raids over the last year. It has become the dominant militant group in the region as a result of these raids.
ISWAP's activities are concentrated around Lake Chad, which borders Nigeria, Cameroon, Chad and Niger.
IS claims attacks in the Lake Chad region through its Amaq news agency. However, the extent of support provided by Islamic State to ISWAP is unclear and many security experts say the relationship is mainly in name rather than direct funding and logistical support.
Numbers are hard to pin down, but analysts put ISWAP's strength at between 5,000 and 18,000.
ISWAP raises money through taxes on traders, smugglers and fishermen in the Lake Chad region. Inducements such as seeds and fertilizer have also been offered to locals.
Egypt has seen no large attacks over the past year, but smaller incidents persist and the military is mounting a campaign against Islamist insurgents, mainly on the Sinai Peninsula.
The military says several hundred militants have been killed since it launched a major campaign in February 2018 to defeat fighters linked to Islamic State in Sinai.
Three civilians and four police personnel were killed this month by a suicide bomber in the North Sinai town of Sheikh Zuweid, the Interior Ministry said. Claiming the attack, IS said 15 people were killed or wounded.
In November, gunmen killed seven Christians on a bus in Minya province, south of Cairo. IS claimed responsibility.
H.A. Hellyer, senior associate fellow at the Royal United Services Institute (RUSI) and the Atlantic Council in London, said IS remains a threat in Egypt via two avenues: in the Sinai Peninsula, where part of the Ansar Bayt al-Maqdis group pledged allegiance to IS years ago; and in sporadic cells elsewhere, made up of more recent recruits and possibly returning fighters from Syria and Iraq.
IS militants have carried out deadly bombings and shootings in Saudi Arabia against security forces and minority Shiite Muslims, after the authorities crushed an al-Qaida insurgency over a decade ago.
Saudi security forces said they foiled an attack by four IS militants north of Riyadh on Sunday, and arrested 13 others on Monday in connection with planning other attacks.
The security forces also raided a house they said the militants were using as a bomb factory, and seized suicide vests, homemade bombs, rifles and IS publications.