New Delhi | India on Tuesday summoned the Russian charge d'affaires (CDA) and lodged a strong protest over the killing of four Indian seafarers aboard a Guinea Bissau-flagged merchant vessel off the coast of Ukraine.

Sources said the Ministry of External Affairs (MEA) told the Russian diplomat that the attack on the merchant vessel, which killed Indians, was unacceptable.

Ukrainian Foreign Minister Andrii Sybiha said Russia attacked the civilian vessel navigating Ukraine's maritime corridor on Sunday and its crew included citizens of Syria and India.

It is the first instance of death of Indian seafarers in the Russia-Ukraine conflict.

The Guinea-Bissau-flagged ship was hit by Russian cruise missiles, the Ukrainian Air Force said.

The vessel -- MV Golden Leo -- had 17 crew members, including five Indian nationals, according to the MEA.

India condemned the attack and reiterated that targeting commercial shipping and endangering innocent civilian crew members is "deplorable and should be avoided".

"On the evening of July 19, the vessel MV Golden Leo was attacked while departing the port of Odesa. At the time of the incident, there were 17 crew members on board, including five Indian nationals," the MEA said on Monday night.

"As per information available, four Indian nationals have tragically lost their lives, while one is hospitalised in a critical condition," it had said.

The MEA said the Indian mission in Ukraine is closely monitoring the situation and is making every effort to extend all possible assistance to those affected.

"We extend our deepest condolences to the families of the deceased Indian nationals and wish the injured Indian national a speedy and full recovery," it said in a statement.

Without directly naming Russia, the MEA had said: "India condemns such attacks and reiterates that targeting commercial shipping and endangering innocent civilian crew members, or otherwise impeding freedom of navigation and commerce, is deplorable and should be avoided."