The Assam government declared a three-day state mourning from Tuesday to condole the death of five policemen and one civilian in a border clash with Mizoram on the previous day, a notification said.

During this period, the national flag will fly at half-mast and there will be no public entertainment, the order issued by the General Administration Department said.

At least six persons were killed and 60 others, including an SP, injured in a bloody clash along the Assam-Mizoram border on Monday.

Union Home Minister Amit Shah has spoken to the chief ministers of Assam and Mizoram, Himanta Biswa Sarma and Zoramthanga respectively, and urged them to ensure peace along the disputed border and find an amicable settlement.

Sarma paid floral tributes to the five slain policemen at Silchar on Tuesday.

"We are deeply anguished by the loss of lives of our brave @assam police personnel. I visited Silchar SP office and paid floral tributes to the five martyrs and salute their sacrifice," he tweeted.

Earlier in the day, the chief minister visited the Silchar Medical College and Hospital and met the police personnel injured in the attack.

"Visited SMCH to meet injured officials and directed doctors to ensure best treatment to them. Asked to send seriously injured personnel for higher level treatment by air ambulance on priority," Sarma said in another Twitter post.

The chief minister is also likely to visit the inter-state border where the situation was stated to be "tense but under control", officials said.