Iranian authorities have blamed fibre-optic network damage for a convenient slow-down in net connection speeds in the country this week.

The slow-down comes suspiciously close to planned opposition demos, timed to coincide with the 11 February anniversary of the Iranian revolution. Opposition groups, supported by many in the West, have used the internet and SMS messages to co-ordinate activities since the disputed re-election of President Ahmadinejad last June.

Government officials blame shipping traffic for damaging Iran's main optic fibre link across the Gulf, between the Iranian port of Jask and Fujairah in the UAE. Internet services and SMS delivery have been severely impaired during the last week. Communications Minister Reza Taghipour told Iran's state broadcaster that the "breakage will be repaired by next week", AFP reports.

It seems unlikely the repairs will be effected before the planned protests. Net filtering in Iran already blocks many sites for political or cultural reasons and this control can be expected to tighten still further in the run-up to Thursday's protests.

In possibly related news, the website of a radio station run by an Iranian dissident group in the Netherlands came under attack by a pro-government group of hackers late last month, Bloomberg reports. Radio Zamaneh's website was hijacked by a group using the name Iran’s Cyber Army for around a day, before control was seized back by the station, which is banned in Iran.

The very similarly named Iranian Cyber Army group used a DNS attack to hijack Twitter back in December, in order to protest against Western interference in Iranian affairs. ®