Belgian police said they had found a suspicious package on a public bus in Brussels and had called in the bomb squad to investigate on the day of the visit of U.S. President Barack Obama.

The package was found in the north of Brussels, about three kms (two miles) from the headquarters of NATO. Obama was due to hold talks with NATO Secretary-General Anders Fogh Rasmussen later.

"We have closed off the surrounding area, which is our standard procedure in such cases," a spokesman for Brussel police said.