NBC, MSNBC AND NEWS SERVICES Oct. 7 - The first wave of military action against Afghanistan's ruling Taliban regime has begun, President Bush announced to the nationSunday at 1 p.m. ET. "The Taliban will pay a price" for harboring terrorists, the president vowed minutes after explosions and anti-aircraft fire were heard in Kabul and electricity was cut throughout city. By 3 p.m. ET, the Pentagon reported that 50 Tomahawk missiles had been fired, joined by 40 bomber and fighter aircraft that targeted sites around several Afghan cities. AT LEAST FOUR loud explosions were heard in Kabul, and the BBC reported that the blasts appeared to have destroyed the city's airport, where the Taliban operates a command center. The Taliban's Defense Ministry reportedly was also hit. Defense Secretary Donald Rumsfeld told reporters at the Pentagon that the strike was ongoing and that targets included Taliban air defense systems and aircraft, as well as sites where "foreign terrorists" were thought to be. Within the first three hours, 50 Tomahawk cruise missiles were fired by U.S. warships and British submarines, he said. In addition, 15 land-based bombers - including B-1s, B-52s and B-2s - were used, as were 5 sea-based fighter jets. "So far, so good," a Pentagon official told NBC News of the initial bombing. British Prime Minister Tony Blair told his nation that the Taliban had been "given the choice of siding with justice or siding with terror, and they chose to side with terror." Other words of support included a Russian statement that Afghanistan had become an "international center of terrorism and extremism" and a safe haven for "terrorists." Explosions were also reported in the eastern Afghan city of Jalalabad, where terrorist training camps are thought to operate, and the southern city of Kandahar, where Taliban leader Mullah Mohammed Omar and other senior Taliban officials live. Other reports said sites around the cities of Herat and Mazar-e Sharif were also targeted. There was no official word from Kabul, but the Taliban's ambassador to Pakistan, Mullah Abdul Salam Zaeef, called the strike a "terrorist" act.