IT IS more than a century since cartographers drew east Africa’s coastal strip as a single territory. A map from 1876 shows “Zanguebar” stretching from what is now southern Somalia to northern Mozambique. In the colonial carve-up that followed, lines were drawn between the port cities of Mombasa and Dar es Salaam and the island of Zanzibar. The Swahili coast, named after a language created by the cohabitation of inland Bantu tribes and Arab traders and slavers, was at various times divided between four colonial countries: Britain, Germany, Italy and Portugal. Their vast possessions in the hinterland eventually became Kenya, Tanzania, Somalia and Mozambique. Yet in terms of culture, religion and geography the coastal strip, especially its swathe in the middle, has retained a distinct identity.

To that now add rising discontent. Inequality, land grabs and corruption have soured many coastal communities in recent years. In radical Islam some now find an outlet for their anger. A spate of apparently unrelated church burnings, riots, disappearances and assassinations has swept the coast. Secessionist sentiment is rising.

In Michenzani district of Stone Town on the island of Zanzibar, which is part of Tanzania, angry slogans decorate mouldy concrete walls denouncing “Muungano”, Swahili for union with the mainland. Since October 16th rioters have repeatedly clashed with police, following the brief disappearance of a popular local cleric. Farid Hadi Ahmed, the leader of Uamsho, or “Awakening”, which has recently evolved from a religious charity into an Islamist political movement, demands independence for Zanzibar, restrictions on alcohol consumption and a dress code for the tens of thousands of foreign tourists visiting the island every year. Political violence is not new to Zanzibar, nor is unease among religious conservatives over the behaviour of holidaymakers. But Uamsho has succeeded in funnelling cultural and political tensions into support for radical Islamism. The group denies involvement in church burning but openly feeds resentment of wabara, or mainland Tanzanians. Supporters are implicated in attacks on bars said to be owned by immigrants. Almas Ali, a history teacher, calls the 1964 union with the mainland a “bad marriage”. A divorce, he says, is long overdue. Grievances include the loss of tax privileges in the 1990s that hit transit trading, and Tanzania’s failure to join the Organisation of Islamic Co-operation, a club of Muslim countries that locals hoped would channel aid to Zanzibar. Islamist hotheads used to support Tanzania’s main opposition party, the Civic United Front (CUF). But in 2010 it formed a unity government with the ruling Revolutionary Party (CCM) following unrest amid accusations of voter fraud. This disappointed many Zanzibari supporters and created a political vacuum on the island. Ismail Jussa, the deputy CUF leader, says, “By the time we woke up, we found ourselves engulfed by this religious group.” Officially unemployment on the islands is 34% but officials at the Zanzibar chamber of commerce say the real rate is much higher, with youth joblessness and underemployment estimated at 85%.

Meanwhile, Kenya’s main port city of Mombasa erupted in August over the murder of a local cleric, Aboud Rogo Mohamed, who was shot in his car by unknown assailants. The cleric, who was barred from travelling to America for alleged links to Somali militants, often visited Islamist forums in Zanzibar.

A banned secessionist group called the Mombasa Republican Council, which has Christian as well as Muslim supporters, won a court battle this year to get legal status. It blames Kenya’s centralised government for coastal poverty. Calling the group a “criminal gang” infested with jihadists, the government violently cracked down; three members of the council were killed when its leader, Omar Hamisi Mwamnuadzi, was arrested on October 15th. One of Kenya’s leading clerics, Sheikh Mohammed Dor, an MP, has since been arrested, accused of seeking to fund secessionists.

Across the border, Tanzania’s business capital, Dar es Salaam, has been rocked by the worst religious riots in years. Churches were looted and burned on October 12th. Sheikh Issa Ponda, a radical cleric, has been arrested and accused of inciting violence. If the secessionist groups up and down the coast link up, they could become a powerful dissident force.

The recent discovery of gas along the coast could make things still worse. Mohamed Hafidh Khalfan, an economist at the State University of Zanzibar, fears a Nigerian-style insurgency, “Poverty is like a fuel that just needs a spark to blow it up.”