Thai police on Saturday questioned witnesses and combed the scene of an assassination attempt on a leading political activist as they faced speculation of state involvement in the attack. The deputy national police chief said they suspected about five men had carried out Friday's gun attack on Sondhi Limthongkul, who led a blockade of the kingdom's main airports last year. "I have asked officials to collect all evidence together, for example bullet casings, and to check CCTV," Jongrak Jutanond told reporters. "Police estimate that there were about five men. I have asked officials to speed up the questioning of witnesses," he said. Colonel King Kwaengwisatchaicharn earlier said that police had questioned a local egg seller whose pick-up truck had been seen in the area, but had quickly ruled out his involvement in the attack. Gunmen wielding AK-47 and M-16 automatic weapons fired about 100 rounds at Sondhi's car in a dawn attack on Friday that wounded him along with his driver and an aide. Doctors said that Sondhi, founder of the "Yellow Shirts" royalist movement that helped topple former premier Thaksin Shinawatra, was recovering well after an operation to remove a bullet fragment from his skull. Sondhi's People's Alliance for Democracy (PAD) said it believed "men in uniform" were to blame, a suspicion echoed by local media. PAD spokesman Suriyasai Katasila said the "daring" attack had been carried out by those "who are not afraid of the law". "I suspect the situation may be more complicated than we think," he said. Thai newspapers the "Daily News" and English-language "The Nation" also speculated that the army had been involved in the attack because of the weapons used to carry it out. But police and government officials played down speculation of involvement by state agencies. Media mogul Sondhi is hated by Thaksin's rival Red Shirts and has enemies among Thailand's business community. "Police are weighing up political and private motivations in this assassination attempt. Police will question Sondhi when he is recovered to hear his side," said Jongrak. "In previous cases civilians have been arrested with heavy weapons. Police cannot say the gunmen were men in uniform because there is no evidence for it yet," he said, adding that extra security had been provided for Sondhi. The speculation worsens the political crisis gripping Thailand, caused by a split between the poorer Red Shirt supporters of Thaksin, who lives in exile to avoid a jail term for graft, and Sondhi's PAD who are backed by the kingdom's elites. Keep up with the latest business news from the region with the daily Emirates Business 24|7 newsletter. To subscribe to the newsletter, please click here .