Dhaka, Nov. 2 -- Police have filed three cases over arson and vandalism during garment workers' protests for higher pay in Gazipur, naming about 4,000 people as suspects.

Industrial Police lodged two of the cases and Gazipur Metropolitan Police (GMP) one over the unrest since Sunday.

Amjad Hossain, superintendent of Industrial Police-2 (Gazipur), said at least 30 people have been arrested.

Workers' protests spread from Sunday morning across Konabari, Kashimpur, Mouchak, Shafipur, Chandra and Palli Bidyut, with protesters blocking the Dhaka-Tangail Highway and halting traffic.

Workers and law enforcers chased each other back and forth. A police box was set on fire in Konabari, and arson and vehicle vandalism followed in the Palli Bidyu...