EASTERN GHOUTA (Reuters) - A tightening siege has pushed people to the verge of famine in the eastern suburbs of Damascus, residents and aid workers say, bringing desperation to the only major rebel enclave near the Syrian capital. Cases of malnutrition among children have almost doubled in the last two months at one clinic in the suburbs, which have been under siege by Syrian government forces since 2013 but come under new pressure this year as tunnels used to smuggle in food have been cut off.