Belgium's capital was under the country's highest terror alert level Saturday -- with Brussels' subway service suspended and people warned to avoid gatherings -- as authorities warned of a possible imminent threat a week after deadly attacks in Paris.<br />Specific reasons for Friday night's alert weren't released, but as news of the heightened security measures spread, so did information about four new arrests tied to the Paris probe -- one in Brussels' Molenbeek suburb, and three in Turkey.<br />The Belgian Interior Ministry's crisis center cited only "a serious and imminent threat" when it announced Brussels' terror alert level was rising to 4, the country's highest.<br />But Belgian Prime Minister Charles Michel authorities had reason to suspect possible attacks in more than one location.<br />"We are talking of a threat of several individuals with weapons and explosives, to launch acts, maybe even in several places at once," Michel told reporters in Brussels on Saturday.
