A suicide and gun attack that killed at least 120 at one of Nigeria's most well-known mosques was extreme in its brutality but part of an increasingly familiar pattern that has spread fear even beyond Nigeria's borders.
Unsuspecting worshippers were blown up as they gathered for Friday prayers at the Grand Mosque in the northern city of Kano; those who survived were cut down by gunfire as they fled.
The attack was widely seen as revenge for the Muslim Emir of Kano's call at the same mosque last week for civilians to arm and protect themselves against Boko Haram.
Nigerian police inspect the site of an explosion in Kano, Nigeria. Multiple explosions tore through the central mosque in Nigeria's second-largest city on Friday. (AP Photo)
"Boko Haram has repeatedly threatened religious and traditional leaders in northern Nigeria, who are seen by the group as allies and instruments of the state," said Andrew Noakes, of the Nigeria Security Network of analysts.
But it was also in keeping with the Islamist group's brutal violence over a greater geographical area in the last few weeks -- and a likely wider strategy to further undermine national and regional security.
"Boko Haram are trying to create the perception that they are anywhere and everywhere," said Ryan Cummings, chief Africa analyst at the Red24 security consultants in Cape Town.
"It almost seems that the trend in the insurgency is reverting to that witnessed in 2012 when it seemed that Boko Haram was expanding rapidly westwards and southwards," he told AFP.
Just hours before the Kano massacre , a suspected remote-controlled roadside bomb, buried in the dirt near another mosque nearly 600 kilometres (375 miles) away in Maiduguri, was defused.
Maiduguri, where Boko Haram was founded in 2002, was already tense after two women blew themselves up within minutes of each other at a crowded market on Tuesday, killing more than 45 shoppers and traders.
The previous day, up to 50 people were killed in Damasak, 180 kilometres north of the city near the border with Niger, when Boko Haram fighters overran the town and ambushed those trying to escape.
Four days earlier, the militants slit the throats of and drowned at least 48 fish vendors in another town near Lake Chad.
Mass casualties from Boko Haram attacks are not a new phenomenon in the extremists' five-year insurgency. More than 13,000 people are thought to have died in total since 2009.
Internally displaced children who fled their homes following an attack by Islamist militants in north east Nigeria run round a soccer ground. Some thousands of people have fled their homes in recent times due to Boko Haram attacks. (AP Photo)
But the regularity of attacks and the widening range of tactics -- from hit-and-run strikes to suicide bombings, holding territory and even, it seems, the new attempt to use Al-Qaeda-style roadside bombs -- marks a shift.
Violence had been concentrated for the last 18 months in the three far northeastern states of Borno, Yobe and Adamawa.
But there have been a string of suicide strikes since June across the wider north.
Neighbouring Cameroon, Niger and Chad are also voicing fears about possible attacks there, particularly as the dry season approaches, which makes natural defences such as rivers easier to breach.
One humanitarian source in Niger described a "psychosis of fear" about attacks in border areas, which this week forced the closure of schools and pharmacies.
Boko Haram is opposed to secular, "Western" style education and has regularly attacked schools, teachers and students.
Earlier this month, 58 schoolboys were killed in Potiskum, northeastern Nigeria, when a suicide bomber blew himself up before morning assembly.
Boko Haram is still holding 219 schoolgirls that it kidnapped in mid-April.
In Cameroon's far north, one military commander said they were "convinced" that Boko Haram's aim to declare a hardline Islamic state "is aimed not only at Nigeria but also at Cameroon".
The group has taken over more than two dozen towns in northeast Nigeria in recent months and declared some part of its caliphate, mirroring a similar declaration by militants in Iraq and Syria.
The Kano bombing and attacks elsewhere could be designed to make any renewed counter-insurgency efforts more difficult, analysts say.
Cameroon, Chad, Niger and Nigeria were supposed to have had a 2,800 troops in place along their borders by November 1, to assist the Nigerian army, which has struggled to put down the rebellion.
But as the year-end approaches, no deployment has been announced.
The Kano attack and others outside its traditional heartland leave Nigeria's authorities with a dilemma.
"It basically stymies the reallocation of resources from such regions to counter-terrorism operations being conducted" in the three worst-affected northeast states, said Cummings.