THIRUVANANTHAPURAM: Restrictions have been tightened in Karnataka and Tamil Nadu in the wake of the increase in the number of Omicron cases. People from Kerala need to produce either a two-dose vaccine certificate or a negative RT-PCR certificate, not older than 72 hours, to enter Tamil Nadu. However, even vaccinated people entering Karnataka need to produce a negative RT-PCR certificate. The Tamil Nadu government has announced night curfew from January 6 and a complete lockdown on Sunday. Devotees will not be allowed to enter places of worship on Friday, Saturday and Sunday. Meanwhile, Karnataka has imposed a weekend lockdown for two weeks till January 19.