The Home Ministry said on Monday that state or Union Territory can not dilute the guidelines issued for the fourth phase of nationwide lockdown that will continue till May 31.

In a communication to the chief secretaries of the states and Union territories, Union Home Secretary Ajay Bhalla said the guidelines for the fourth phase of the lockdown were issued after taking the views of the states, following a video-conference held by Prime Minister Narendra Modi with chief ministers on May 11.

"As emphasised in my earlier letters, I would like to reiterate again that States and Union Territories cannot dilute restrictions imposed vide the aforesaid guidelines issued by MHA. States and UTs, based on their assessment of the situation, may prohibit certain other activities in various zones, or impose such restrictions as deemed necessary."

"I would urge you to ensure compliance of the new guidelines and direct all concerned authorities for their strict implementation," Bhalla said in his letter to the chief secretaries on Sunday night," the letter read.

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Bhalla said under the new guidelines effective from Monday, the states and Union territories will categorise "red", "orange" and "green" zones taking into consideration the revised guidelines issued by the Ministry of Health and Family Welfare on Sunday.

Inside the red and orange zones, containment and buffer zones will be identified by the district administration and local urban bodies with technical inputs at the local level and by taking into consideration the health ministry guidelines.

Within the containment zones, strict perimeter control shall be maintained and no movement of persons will be allowed across the zones, except for medical emergencies and maintaining the supply of essential goods and services, the letter said.

The home secretary said a limited number of activities will continue to remain prohibited throughout the country.

The ongoing nationwide lockdown to curb the spread of coronavirus was extended till May 31 by the National Disaster Management Authority on Monday.

New guidelines on lockdown measures have been issued in supersession of the earlier lockdown orders, except the Standing Operating Procedures (SOPs) issued on the movement of persons.

In order to facilitate the movement of persons, various modes of transport have already been opened up in accordance with the SoPs issued by the MHA and all other activities will be permitted, except those specifically prohibited under these guidelines.

However, only essential activities shall be allowed in the COVID-19 containment zones.

The lockdown announced by the prime minister came into effect on March 25 for 21 days initially. It was first extended till May 3 and then again till May 17. On Monday, the lockdown was extended till May 31.