New Delhi: India on Tuesday summoned a Russian diplomat over the killing of four Indian nationals aboard a commercial vessel that came under attack off the coast of Ukraine, according to sources cited by PTI.

The four Indians were among those killed after the merchant vessel MV Golden Leo was struck while departing Ukraine's port of Odesa on Sunday. One more Indian crew member remains in a critical condition.

According to the Ministry of External Affairs (MEA), the vessel had 17 crew members on board, including five Indian nationals, when it came under attack.

Condemning the incident, India said attacks on commercial shipping and civilian crew members were unacceptable.

"As per the information available, four Indian nationals have tragically lost their lives, while one is hospitalised in a critical condition. Our Mission in Ukraine is closely monitoring the situation and is making every effort to extend all possible assistance to those affected," the MEA said in a statement.

The government also reiterated that targeting commercial vessels, endangering civilian seafarers and disrupting freedom of navigation and international trade was deplorable and should be avoided.

Among those killed was Akhil Joyan, a 26-year-old Merchant Navy officer from Vellarikkundu in Kerala's Kasaragod district.

Akhil had returned home on leave last month, got engaged and had resumed duty only a month ago. His family learnt of his death through an email from the shipping company on Monday.

The family said on Tuesday that they have no information on when his mortal remains can be brought back home.