Imphal, Sep 8 : A moderate intensity earthquake, measuring 5.1 on the Richter Scale, hit Manipur's Ukhrul district and adjoining areas late on Monday night, the National Centre for Seismology (NCS) said. NCS said that the moderate intensity tremor, which struck shortly after 11 p.m. on Monday night, was felt in Ukhrul and adjoining districts along Myanmar and Nagaland. The quake struck at a depth of 20 km from the surface. Manipur Disaster Management Authority said that there was no immediate report of any casualty or damage to property. Successive earthquakes in the mountainous northeastern states, especially in Assam, Mizoram and Manipur, have kept the authorities worried, forcing them to build quake-protective structures. Seismologists consider the northeastern region as the sixth most earthquake-prone belt in the world. /IANS