Doctors take out a protest rally in Kolkatta, India, Friday, June 14, 2019. The doctors who were on strike since June 11 were protesting after two of their colleagues were attacked and seriously injured by family members of a patient. During the rally they demanded adequate security and protection for them in the hospitals. (AP Photo/Bikas Das)

New Delhi - Thousands of doctors went on a strike across several Indian cities Friday demanding better security after a junior doctor was attacked in a Kolkata hospital leaving him with serious head injuries.

Hospitals in West Bengal state, of which Kolkata is capital, were the worst-hit as junior doctors who form the backbone of the health services struck work and held protest marches, NDTV news channel reported.

The agitation spread to Delhi, Mumbai, Hyderabad and Patna among other cities where doctors struck work and held rallies.

The Indian Medical Association said 350,000 doctors had joined the strike.

In most places emergency services continued to function, while out-patient services were primarily affected. Long lines of patients could be seen waiting at Delhi's All India Institute of Medical Sciences (AIIMS).

In several hospitals like the SMS Hospital in Jaipur doctors wore black bands and helmets to work.

Paribaha Mukhopadhyaya, a junior doctor at Kolkata's NRS Hospital was attacked on Monday after a patient died, police said.

Family members alleged he had died due to negligence and accompanied by a mob attacked and critically injured Mukhopadhyaya.

Five people in connection with the incident and investigations are on, a spokesman for Kolkata Police said.

The protests snowballed after West Bengal chief minister Mamata Banerjee said Thursday she would take severe action against the doctors if they did not return to work.

Federal Health Minister Harsh Vardhan appealed to the doctors to end their strike in the larger interests of society and hold symbolic protests instead. The government was committed to their security, he said in a Twitter post.