ICAO Doc 4444 says
"5.8.3 Departing aircraft
5.8.3.1 A minimum separation of 2 minutes shall be applied between a LIGHT or MEDIUM aircraft taking off behind a HEAVY aircraft or a LIGHT aircraft taking off behind a MEDIUM aircraft when the aircraft are using:
a) the same runway;
b) parallel runways separated by less than 760 m (2 500 ft);
c) crossing runways if the projected flight path of the second aircraft will cross the projected flight path of the first aircraft at the same altitude or less than 300 m (1 000 ft) below;
d) parallel runways separated by 760 m (2 500 ft) or more, if the projected flight path of the second aircraft will cross the projected flight path of the first aircraft at the same altitude or less than 300 m (1 000 ft) below.
5.8.3.2 A separation minimum of 3 minutes shall be applied between a LIGHT or MEDIUM aircraft when taking off behind a HEAVY aircraft or a LIGHT aircraft when taking off behind a MEDIUM aircraft from:
a) an intermediate part of the same runway; or
b) an intermediate part of a parallel runway separated by less than 760 m (2 500 ft)."
Unfortunately I don't think ICAO says what intermediate means. But in the UK if there are two runway entry points within a short distance the CAA may approve procedures so that they can be considered to be the same for departure separation purposes.