Context :

Aims : In this paper we present new high sensitivity 153 MHz Giant Meterwave Radio Telescope follow–up observations of the diffuse steep spectrum cluster radio sources in the galaxy clusters Abell 521 , Abell 697 , Abell 1682 .
Abell 521 hosts a relic , and together with Abell 697 it also hosts a giant very steep spectrum radio halo .
Abell 1682 is a more complex system with candidate steep spectrum diffuse emission .

Methods : We imaged the diffuse radio emission in these clusters at 153 MHz , and provided flux density measurements of all the sources at this frequency .
Our new flux density measurements , coupled with the existing data at higher frequencies , allow us to study the total spectrum of the halos and relic over at least one order of magnitude in frequency .

Results : Our images confirm the presence of a very steep “ diffuse component ” Â in Abell 1682 .
We found that the spectrum of the relic in Abell 521 can be fitted by a single power–law with \alpha = 1.45 \pm 0.02 from 153 MHz to 5 GHz .
Moreover , we confirm that the halos in Abell 521 and Abell 697 have a very steep spectrum , with \alpha = 1.8 - 1.9 and \alpha = 1.52 \pm 0.05 respectively .
Even with the inclusion of the 153 MHz flux density information it is impossible to discriminate between power–law and curved spectra , as derived from homogeneous turbulent re–acceleration .
The latter are favored on the basis of simple energetic arguments , and we expect that LOFAR will finally unveil the shape of the spectra of radio halos below 100 MHz , thus providing clues on their origin .

Conclusions :