A global ransomware attack on Tuesday hit computers at Russia's biggest oil company, Ukraine's international airport, global shipping firm A.P. Moller-Maersk and the world's biggest advertising agency WPP .

Following is a list of companies and organisations that have reported being hit by cyber attacks:

ROSNEFT

Russia's top oil producer Rosneft said its servers had been hit been a large-scale cyber attack but its oil production was unaffected.

A.P. MOLLER-MAERSK

Danish shipping giant A.P. Moller-Maersk, which handles one out of seven containers shipped globally, said a cyber attack had caused outages at its computer systems across the world.

Maersk's port operator APM Terminals was also hit. Dutch broadcaster RTV Rijnmond reported that 17 shipping container terminals run by APM Terminals had been hacked, including two in Rotterdam and 15 in other parts of the world.

WPP

Britain's WPP, the world's biggest advertising company, said computer systems within several of its agencies had been hit by a suspected cyber attack.

MERCK & Co.

Pharmaceutical company Merck & Co. said in a tweet its computer network was compromised as part of a global hack.

RUSSIAN BANKS

Russia's central bank said there had been “computer attacks" on Russian banks and that in isolated cases their IT systems had been infected.

All Russian branches of Home Credit consumer lender are closed because of a cyber attack, an employee of a Home Credit call centre in Russia said.

UKRAINIAN BANKS, POWER GRID

A number of Ukrainian banks and companies, including the state power distributor, were hit by a cyber attack that disrupted some operations, the Ukrainian central bank said.

UKRAINIAN INTERNATIONAL AIRPORT

Yevhen Dykhne, director of the capital's Boryspil Airport, said it had been hit. “In connection with the irregular situation, some flight delays are possible,” Dykhne said in a post on Facebook.

SAINT GOBAIN

French construction materials company Saint Gobain said it had been a victim of a cyber attack, and it had isolated its computer systems to protect data.

DEUTSCHE POST

German postal and logistics company Deutsche Post said systems of its Express division in the Ukraine have in part been affected by a cyber attack.

METRO

Germany's Metro said its wholesale stores in the Ukraine had been hit by a cyber attack and the retailer was assessing the impact.

MONDELEZ INTERNATIONAL

Food company Mondelez International said employees in different regions were experiencing technical problems but it was unclear whether this was due to a cyber attack.

EVRAZ

Russian steelmaker Evraz said its information systems had been hit by a cyber attack but its output was not affected.

NORWAY

A ransomware cyber attack is taking place in Norway and is affecting an unnamed international company, the Nordic country's national security authority. (Editing by David Clarke)