Jakarta – Several flights were delayed or diverted Tuesday after smoke haze from forest and ground fires blanketed Pekanbaru city on Indonesia's Sumatra island, officials said. The haze is an annual dry-season hazard in parts of Indonesia, despite laws banning the use of fire to clear land for cultivation. It spread to much of Southeast Asia in 1997.

Daryono, from the Riau province Environmental Impact Control office, blamed fires set by large forest and plantation concession-holders as well as by small farmers.

The meteorology office in Pekanbaru said some flights were unable to land or take off but gave no figure. It said visibility was between 300 and 500 meters. Antara news agency said at least seven flights could not land while another flight failed to take off.

Yohannes Drajat of the Pekanbaru meteorology office said satellite imaging on Monday showed "hot spots" – indicating possible fires – on the outskirts of the city and in two other districts.