New Delhi, May 2 -- Rising diesel prices linked to the Iran war are adding urgency to a shift already underway across Africa to move cellphone towers off fossil fuels and onto solar power.

Diesel, which powers the majority of Africa's roughly 500,000 telecommunications towers, has become more expensive and sometimes harder to secure in recent weeks as global fuel markets tightened following the conflict. Several African countries that rely heavily on imported fuel have reported price spikes and supply disruptions, prompting governments and companies to reassess energy strategies.

The transition to cleaner power for the towers that provide cellphone service predates the latest price shocks, driven by cost pressures and climate goals. But...