Officials say recovery from the floods -- the worst to hit the Balkans in more than a century -- is expected to cost billions.
In Bosnia, authorities say they fear the damage may exceed that caused by the entire 1992-95 war.
The European Union said on May 21 that it was likely that Serbia will qualify for EU disaster funds.
Water began receding in some areas on May 21, but the situation remains tense elsewhere, in particular in Belgrade, where a flood peak is expected later in the week.
A landmine dislodged by the flooding exploded in Bosnia on May 21, one of the more than 120,000 mines left over from the war. No one was hurt.