Not long ago, Chinese engineers were putting the finishing touches to two expensive rail projects in east Africa, one linking Djibouti on the Red Sea to landlocked Ethiopia and the other running from the Kenyan port of Mombasa to the capital, Nairobi.

But less than 18 months after both lines were inaugurated with grandiose talk of Chinese-led east African integration, doubts are emerging about their economic viability. The $4.5bn Djibouti-Addis Ababa line, the first fully electrified cross-border railway in Africa, has run into financial and operational difficulties, while the $3.2bn Kenya route is losing money and has been plagued by scandal.