A major police manhunt is underway in Berlin after a man was seriously wounded in a knife attack at the city's Holocaust Memorial.

The man is said to have been injured by a sharp object at around 6pm local time (5pm in the UK) - and has been taken to hospital by emergency services, according to local reports.

A Berlin police spokesman said a "major operation" had been triggered following the attack at the memorial - which sits just next to the US embassy.

The alleged attacker is reported to be on the run - with police preparing a major manhunt.

Meanwhile, police have sealed off the site and are carrying out a search, German outlet Tagesspiegel reported.

It comes mere hours after a teenager was arrested on suspicion of planning an attack on the Israeli embassy in the German capital.

The teen - an 18-year-old from Chechnya, in Russia - had been trying to leave Germany from Berlin's Brandenburg Airport when he was detained, according to Bild.

Bild said the investigation had been the result of a tip-off from a foreign intelligence agency.