  We present a study of diffuse extended ionised gas toward three clouds
located in the Galactic Centre (GC). One line of sight (LOS) is toward the 20
km s$^{-1}$ cloud (LOS$-$0.11) in the Sgr A region, another LOS is toward the
50 km s$^{-1}$ cloud (LOS$-$0.02), also in Sgr A, while the third is toward the
Sgr B2 cloud (LOS+0.693). The emission from the ionised gas is detected from
H$n\alpha$ and H$m\beta$ radio recombination lines (RRLs). He$n\alpha$ and
He$m\beta$ RRL emission is detected with the same $n$ and $m$ as those from the
hydrogen RRLs only toward LOS+0.693. RRLs probe gas with positive and negative
velocities toward the two Sgr A sources. The H$m\beta$ to H$n\alpha$ ratios
reveal that the ionised gas is emitted under local thermodynamic equilibrium
conditions in these regions. We find a He to H mass fraction of 0.29$\pm$0.01
consistent with the typical GC value, supporting the idea that massive stars
have increased the He abundance compared to its primordial value. Physical
properties are derived for the studied sources. We propose that the negative
velocity component of both Sgr A sources is part of gas streams considered
previously to model the GC cloud kinematics. Associated massive stars with what
are presumably the closest HII regions to LOS$-$0.11 (positive velocity gas),
LOS$-$0.02 and LOS+0.693 could be the main sources of UV photons ionising the
gas. The negative velocity components of both Sgr A sources might be ionised by
the same massive stars, but only if they are in the same gas stream.
