JAKARTA: Indonesian rescuers are struggling to reach survivors on Sumatra island after torrential rains unleashed flash floods and triggered landslides, killing dozens of people and displacing thousands of others, authorities said on Thursday. 

Days of relentless rainfall caused rivers in North Sumatra province to overflow, sending waves of mud, rocks and uprooted trees through villages in at least nine regencies, with districts of Sibolga and Central Tapanuli among the hardest hit.   

Communication lines were down in hundreds of sites across North Sumatra, according to the ministry of communications and digital affairs, while ongoing rescue and relief efforts were hampered as access to some districts remained cut off. 

“With the floods and landslides in North Sumatra, chiefs in the affected regions have now declared a state of emergency,” Suharyanto, who heads the National Disaster Mitigation Agency, or BNPB, told reporters in Jakarta. 

“(We will focus) first on opening access, there are roads linking Sibolga to Central Tapanuli and South Tapanuli that are still blocked … we will try to open (them) in one or two days.” 

As of Thursday afternoon, some areas were still flooded while other roads were still blocked by landslide debris, said BNPB spokesman Abdul Muhari. 

At least 6,000 families were affected by the disasters, about half of whom were evacuated and are staying in shelters, while data from local authorities show that the death toll has jumped to at least 43, with 88 others missing. 

Widely circulated footage and photos from the past few days show rapid currents of water overflowing in different parts of the region, as residents stood on the roofs of their submerged houses. 

In some neighborhoods, flash floods surged so quickly that streets turned into violent currents carrying tree trunks, household items and rubble. 

Floods and landslides also affected neighboring provinces of West Sumatra and Aceh, with more rain expected in the next few days due to extreme weather, according to Indonesia’s meteorological agency. 

The floods in Indonesia are one of a series of disasters to hit Southeast Asia this past week. 

Parts of southern Thailand were battling record floods, which have killed at least 33 people and affected more than 2.5 million others. Only about 13,000 have reportedly been evacuated to shelters, as the vast majority are cut off and unable to get help. 

In Malaysia, floods forced the evacuation of about 30,000 people in seven states, including worst-hit Kelantan, which borders Thailand. 

Officials are bracing for more heavy rain for the rest of the week caused by a rare tropical storm that formed in the Malacca Strait, according to a forecast by Malaysia’s meteorological department.