Egypt's kung fu champion has been suspended by his national federation for wearing a T-shirt emblazoned with a symbol associated with opposition to the Egypt's army-backed interim government.

Mohamed Youssef is the latest Egyptian to be censored for wearing the yellow Rabaa sign – a four-fingered salute that honours the hundreds of Islamists killed during August's Rabaa al-Adawiya massacre – as authorities attempt to stamp out opposition Islamist movements.

Youssef wore the T-shirt as judges presented him with a gold medal at an international championship in Russia. In response, a spokesman for Egypt's kung fu association told state media that Youssef had been flown home early, suspended from competition and barred from taking part in a kung fu tournament next month in Malaysia.

Egypt's establishment appears to be deeply irked by the Rabaa symbol, which has been drawn on walls across the country and displayed by supporters of the deposed Islamist president Mohamed Morsi since the August massacre. Three men were arrested in September for creating T-shirts carrying the symbol, while a schoolboy was later photographed being detained while forming a version of the logo with his right hand.

The sign has gained currency among Islamists across the world, with many overseas supporters of Morsi displaying it on their social media profiles, or in person at protests. Turkey's prime minister, Recep Tayyip Erdoğan, has also been pictured displaying the four-fingered salute. In Jordan, an ally of Egypt's new secular-minded regime, three protesters were arrested for carrying a version of the symbol – an act, a Jordanian official said, "that would harm Jordan's relations with a brotherly Arab country".

The non-religious nature of the Rabaa sign has been perceived as an attempt to appeal to secular opponents of Egypt's military-backed government, but so far it used almost exclusively by Islamist supporters of Morsi.

The government crackdown on displaying the symbol has been interpreted as part of a wider campaign to drive Morsi's backers from the public arena. More than 1,000 of his supporters have been killed by state officials since his overthrow in July, and thousands more have been arrested and detained without charge. Only a handful of the leaders of Morsi's Muslim Brotherhood operate openly since the group's activities were banned by government order in September.

Under the current interim government, police have also raided the offices of several well known secular activists, and others have been smeared by state newspapers.

On Tuesday, Egyptian media reported that the attorney general had launched an investigation into the country's best-known television satirist, Bassem Youssef, only four days after the comedian returned to the airwaves for the first time since Morsi was ousted.

Bassem Youssef's spokesman told the Guardian there had been no official confirmation of the news, but should it be confirmed, it would mark a much swifter censorship of the comedian than under Morsi. Youssef was also investigated during Morsi's tenure, but the former president's prosecutors took months to enact the procedures.