BEIJING, Aug 22 (Reuters) - Two cities in China"s central province of Henan issued highest flood warnings on Sunday, calling for local agencies to prepare for torrential rains, state television reported. Xingyang and Changyuan in Henan, a transportation hub for China, raised their flood-control response levels to I from II, the top of China’s four-tier scale, warning of possible dam collapses and extraordinary simultaneous floods. This summer"s rains are adding pressure on the world"s second-largest economy, already struggling with sporadic cases of Delta strain of coronavirus. Record rainfall in Henan last month caused floods that killed more than 300 people and caused suspended production at factories. Xingyang and Changyuan are in some of the areas hardest-hit last month. On Sunday the province red alerts of torrential rains for multiple regions, the strongest indicator on China"s four-color scale, forecasting more than 100 mm (4 inches) within three hours. Henan also suspended port and wharf production. Trains in and out of provincial capital Zhengzhou are partially delayed or cancelled. More cities in the province have announced suspension of school, public transportation, factory and business activities until Monday evening. China has warned of heavy rain nationwide, including Sichuan province in the southwest and Heilongjiang in the northeast.