The driver for a Russian-Israeli businessman who was gunned down in a Moscow attack is in grave condition, medical sources said.

Pyotr Tumanov was seriously hurt when unidentified gunmen drove up to his parked Mercedes Monday and opened fire on his passenger, businessman Shabtai von Kalmanovich, who was killed instantly. An unnamed hospital source told RIA Novosti Tuesday that Tumanov was in intensive care and that security in the ward had been tightened.

The Russian news service said Tumanov initially gave chase to the gunmen after the shooting on Moscow's Krasnopresnenskaya Embankment, but had to pull over due to his injuries.

Police investigators say the gunmen, who used a 9mm automatic and a pump-action shotgun, looked to be contract killers and did not rule out the possibility the slaying was an assassination in connection with Kalmanovich's business activities.

RIA Novosti said Kalmanovich, who was born in Soviet Lithuania, emigrated to Israel in 1972. He returned to post-Soviet Russia in 1993 after being convicted in Israel of spying for the Soviet Union, and prospered in chaotic early days of Russian capitalism.